An apparatus for determining the gas permeability of a material by gas chromatography

Abstract

The application discloses a device for determining gas permeability by gas chromatography, which comprises a test chamber, a shell, a test box, a carrier gas temperature control device, a test gas temperature control device, a first carrier gas pipe, a first test gas pipe, a first molecular sieve, a second molecular sieve, a second carrier gas pipe, a second test gas pipe, a third carrier gas pipe, a third test gas pipe, a fourth carrier gas pipe, a fourth test gas pipe, a carrier gas inlet connecting pipe, a test gas inlet connecting pipe, a carrier gas outlet connecting pipe, a test gas outlet connecting pipe, a fifth carrier gas pipe, a fifth test gas pipe, a sixth carrier gas pipe, a quantitative ring and a gas chromatograph. The device for determining gas permeability by gas chromatography is rationally structured, gas permeability can be determined by gas chromatography, the device is accurate, suitable for various gases, simple and convenient to operate, does not require special professional skills, has high test efficiency, is compact and reasonable in structure, small in size, flexible, convenient to disassemble and assemble and convenient to maintain.

Description

Technical Field

[0001] This invention relates to an apparatus for determining gas permeability using gas chromatography, belonging to the technical field of packaging material performance testing. Background Technology

[0002] Plastic packaging for food has become an integral and important part of the food industry. It plays a vital role in ensuring food quality and hygiene, preserving original components and nutrients, facilitating storage and transportation, promoting sales, extending shelf life, and increasing product value. Due to the excellent properties of plastic materials, such as light weight, good chemical stability, ease of processing and decoration, and excellent food protection, their application in food packaging is widespread. In particular, the barrier properties of plastic films against gases such as oxygen and carbon dioxide play a crucial role in food preservation.

[0003] Existing technologies often employ differential pressure methods to detect the gas barrier properties of packaging films. However, differential pressure detectors cannot detect samples with high barrier properties, and their accuracy is also low. Some institutions use coulometric detectors to test the gas barrier properties of packaging films; however, since coulometric detectors are only applicable to oxygen, only oxygen can be tested, and the detection accuracy is low. Therefore, the inventors have designed the gas chromatography apparatus for determining gas permeability, applicable to a variety of gases. Summary of the Invention

[0004] This invention provides a device for determining gas permeability by gas chromatography, which realizes the gas chromatography determination of gas permeability with high accuracy, realizes trace testing, and is applicable to various gases; it has a compact and reasonable structure and a small and flexible size.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] An apparatus for determining gas permeability by gas chromatography includes a test chamber, a housing, a test box, a carrier gas temperature control device, a test gas temperature control device, a first carrier gas tube, a first test gas tube, a first molecular sieve, a second molecular sieve, a second carrier gas tube, a second test gas tube, a third carrier gas tube, a third test gas tube, a fourth carrier gas tube, a fourth test gas tube, a carrier gas inlet connection tube, a test gas inlet connection tube, a carrier gas outlet connection tube, a test gas outlet connection tube, a fifth carrier gas tube, a fifth test gas tube, a sixth carrier gas tube, a quantitative loop, and a gas chromatograph.

[0007] The test chamber is located inside the outer shell on the right side, and the test box is located inside the test chamber. There are two or more test boxes with the same structure (i.e., there are two or more test boxes, and all of them are identical). The test box includes a left box and a right box. The left box has a left chamber on the right side, and the right box has a right chamber on the left side. The left and right box chambers are movably connected together (i.e., the left and right chambers are facing each other, and when the test membrane is not installed, they are interconnected and form a complete cavity). There is a seal between the left and right boxes, and the left and right chambers are connected to form a connected and sealed air cavity. There is a carrier gas inlet connector on the outer bottom of the left box and a carrier gas outlet connector on the outer top of the left box. There is a test gas inlet connector on the outer bottom of the right box and a test gas outlet connector on the outer top of the right box. There are interlocking anti-misalignment structures on the left and right boxes.

[0008] The carrier gas temperature control device and the test gas temperature control device are located on the left side wall inside the outer shell. One end of the third carrier gas pipe is connected to the inlet of the carrier gas temperature control device, and the other end extends out of the side wall of the outer shell to form a carrier gas inlet. One end of the first carrier gas pipe is connected to the carrier gas source, and the other end is connected to the inlet of the first molecular sieve. One end of the second carrier gas pipe is connected to the outlet of the first molecular sieve, and the other end is connected to the carrier gas inlet. One end of the fourth carrier gas pipe is connected to the outlet of the carrier gas temperature control device, and the other end is connected to the inlet of the carrier gas inlet connecting pipe. The carrier gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet branches of the carrier gas inlet connecting pipe are two or more carrier gas inlet branch pipes. The number of carrier gas inlet branch pipes is equal to the number of test chambers and corresponds one-to-one. The carrier gas inlet branch pipes extend into the test chamber and are connected to the carrier gas inlet connector on the corresponding test chamber.

[0009] The third test gas tube connects to the inlet of the test gas temperature control device at one end and extends through the side wall of the outer shell to form a test gas inlet at the other end. The first test gas tube connects to the test gas source at one end and to the inlet of the second molecular sieve at the other end. The second test gas tube connects to the outlet of the second molecular sieve at one end and to the test gas inlet at the other end. The fourth test gas tube connects to the outlet of the test gas temperature control device at one end and to the inlet of the test gas inlet connecting pipe at the other end. The test gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet branches of the test gas inlet connecting pipe are two or more test gas inlet branch pipes. The number of test gas inlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas inlet branch pipes extend into the test chamber and are connected to the test gas inlet connector on their corresponding test boxes.

[0010] Both the carrier gas outlet connection pipe and the test gas outlet connection pipe are installed on the top of the test chamber. The inlet branches of the carrier gas outlet connection pipe are two or more carrier gas outlet branch pipes. The number of carrier gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The carrier gas outlet branch pipes extend into the test chamber and are connected to the carrier gas outlet connector on their corresponding test boxes. The inlet branches of the test gas outlet connection pipe are two or more test gas outlet branch pipes. The number of test gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas outlet branch pipes extend into the test chamber and are connected to the test gas outlet connector on their corresponding test boxes.

[0011] One end of the fifth carrier gas tube is connected to the outlet of the carrier gas outlet connection tube, and the other end extends through the side wall of the outer shell to branch into a carrier gas venting tube and a carrier gas test tube; one end of the fifth test gas tube is connected to the outlet of the test gas outlet connection tube, and the other end extends through the side wall of the outer shell to form a test venting tube.

[0012] One end of the sixth carrier tube is connected to the fourth carrier tube, and the other end is connected to the fifth carrier tube;

[0013] The carrier gas test tube, quantitative loop, and gas chromatograph are connected in sequence via tubing.

[0014] The aforementioned first and second molecular sieves, serving as drying equipment, are used to absorb small amounts of moisture in the gas, improving measurement accuracy. The carrier gas temperature control device and the test gas temperature control device are used to control the corresponding gas within the required range. The carrier gas temperature control device and the test gas temperature control device have the same structure, with a gas chamber inside the temperature control device. The gas chamber has an inlet and an outlet, and a temperature control device for cooling and heating is located around the gas chamber. The gas chamber is preferably a serpentine cavity structure, with one end of the serpentine cavity being the inlet and the other end being the outlet.

[0015] The directional terms such as left and right, top and bottom in this application refer to the relative positions of each component. The left and right are reversed for the sake of convenience and do not affect the substance of the solution in this application, and are also within the scope of protection of this application.

[0016] In the existing technology, the main method for determining gas permeation is the coulometric detector method, which has lower accuracy than gas chromatography. Gas chromatography can perform trace tests and has higher accuracy.

[0017] To simplify the equipment and facilitate assembly, the test chamber includes a first support plate, a second support plate, and a third support plate. The first support plate is installed at the bottom of the test chamber via a first telescopic rod. The third support plate is pressed against the side wall of the test chamber, and the second support plate is installed on the third support plate via a second telescopic rod. The first and second support plates are parallel and opposite to each other, and the space between the first and second support plates forms the test chamber. The distance between the first and second support plates can be adjusted by extending and retracting the first and / or second telescopic rods, thereby enabling the disassembly and assembly of the test chamber. An entrance / exit is provided on the outer shell facing the test chamber, and a sealed door is movably connected to the entrance / exit to facilitate the removal and installation of the test chamber.

[0018] To improve stability during use, the carrier gas inlet connection pipe, test gas inlet connection pipe, carrier gas outlet connection pipe, and test gas outlet connection pipe are all made of copper. The carrier gas inlet connection pipe and the test gas inlet connection pipe are welded to the first support plate, and the carrier gas outlet connection pipe and the test gas outlet connection pipe are welded to the second support plate.

[0019] To improve airtightness and facilitate operation, pneumatic telescopic rods are installed on the left side of the left chamber and the right side of the right chamber of the test chamber. These are used to clamp the sample. The direction from left to right on the test chamber is perpendicular to the direction from top to bottom.

[0020] As a preferred embodiment, the anti-misalignment structure includes at least two positioning rods located around the right side of the left housing, at least two positioning through holes located around the left side of the right housing, and a pin. The number of positioning rods is equal to the number of positioning through holes and corresponds one-to-one. The height of the positioning rods is greater than the depth of the positioning through holes. The positioning rods have elongated holes arranged axially. When the left and right housings are movably connected together, the seal between the left and right housings (the seal has a layer of sealing grease) is under compression. The positioning rods are movably inserted into the corresponding positioning through holes and extend beyond the corresponding positioning through holes. The pins are movably inserted into the elongated holes of the corresponding positioning rods that extend beyond the positioning through holes. After the pins are inserted, the left and right sealing rings remain under compression. This prevents misalignment while also providing effective fixation. Furthermore, the elongated holes on the pins do not affect the clamping of the pneumatic telescopic rods on the left and right housings.

[0021] To improve temperature uniformity within the housing and thus enhance testing accuracy, cavity temperature control devices are installed at the bottom left and top right sides of the housing for temperature control within the housing. These temperature control devices are readily available commercially available products.

[0022] The control circuit is located on the top left side inside the outer casing. The cavity temperature control device, the carrier gas temperature control device, and the test gas temperature control device are all connected to the control circuit. The structure and connection method of the control circuit are based on the existing technology. This application has not made any improvements to this, so it will not be described in detail here.

[0023] For ease of disassembly, assembly, handling, and storage, the apparatus for determining gas permeability using gas chromatography also includes a carrier gas inlet transition tube, a test gas inlet transition tube, and a carrier gas outlet transition tube. The two ends of the carrier gas inlet transition tube are connected to the carrier gas inlet and the second carrier gas tube via quick-connect structures, and a first pressure gauge is installed on the carrier gas inlet transition tube. The two ends of the test gas inlet transition tube are connected to the test gas inlet and the second test gas tube via quick-connect structures, and a second pressure gauge is installed on the test gas inlet transition tube. The two ends of the carrier gas outlet transition tube are connected to the metering loop and the carrier gas test tube via quick-connect structures. The quick-connect structures are also known as fast-plug connections, facilitating rapid assembly and disassembly.

[0024] For ease of maintenance, the two ends of the fourth carrier gas tube are connected to the outlet of the carrier gas temperature control device and the inlet of the carrier gas inlet connecting pipe via quick-connect structures, and the fourth carrier gas tube is equipped with a first flow meter; the two ends of the fourth test gas tube are connected to the outlet of the test gas temperature control device and the inlet of the test gas inlet connecting pipe via quick-connect structures, and the fourth test gas tube is equipped with a second flow meter. This facilitates quick disassembly, assembly, inspection, and maintenance.

[0025] For ease of control, the fourth test gas tube is equipped with an inlet three-way valve, the fourth carrier gas tube is equipped with an inlet four-way valve, and the fifth carrier gas tube is equipped with an outlet four-way valve. The three ports on the inlet three-way valve are defined as the first port A, the second port A, and the third port A, respectively. The four ports on the inlet four-way valve are defined as the first port B, the second port B, the third port B, and the fourth port B, respectively. The four ports on the outlet four-way valve are defined as the first port C, the second port C, the third port C, and the fourth port C, respectively. The first port A and the second port A are connected to the fourth test gas tubes on both sides, the third port A is connected to the first port B through a pipeline, the second port B and the third port B are connected to the fourth carrier gas tubes on both sides, the two ends of the sixth carrier gas tube are connected to the fourth port B and the first port C, the second port C and the third port C are connected to the fifth carrier gas tubes and the carrier gas test tube on both sides, respectively, and the fourth port C is connected to the carrier gas venting pipe. This allows for the creation of the required air path by controlling the valves, resulting in a simple structure and convenient use.

[0026] The apparatus described above for determining gas permeability by gas chromatography can form the following gas path:

[0027] Gas path 1: The test gas flows sequentially through the second molecular sieve, the second pressure gauge, the test gas temperature control device, the second flow meter, and the right chamber before being vented.

[0028] Gas path 2: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, the left chamber and the metering loop, and then enters the gas chromatograph;

[0029] Gas path 3: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device and the metering loop before entering the gas chromatograph;

[0030] Gas path 4: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter and the left chamber, and then is vented.

[0031] Gas path 5: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, and the right chamber before being vented.

[0032] Gas path 1 and gas path 2 are the flow directions of the test gas and the carrier gas during testing. Gas path 2 is used to measure the content of the test gas in the carrier gas and to calculate the gas permeation rate.

[0033] Gas path 3 contains the amount of test gas in the carrier gas, which serves as the zero point for calculation;

[0034] Gas path 4 is used to purge the left chamber with carrier gas before testing, and gas path 5 is used to purge the right chamber with carrier gas before testing. At this time, the test gas does not flow.

[0035] When the above-mentioned apparatus for determining gas permeability by gas chromatography is used to test the gas permeability of the membrane under test, the test method includes the following steps:

[0036] 1) Place the membrane to be tested between the left and right chambers, and connect the left and right chambers together. The membrane to be tested is placed in the left chamber on one side and the right chamber on the other side. Then, put the test box with the membrane to be tested into the test chamber and connect the corresponding pipeline.

[0037] 2) Open air passage 4, close the other air passages, and purge the left chamber with carrier gas;

[0038] 3) Open gas path 5 and close the other gas paths. Purge the right chamber with carrier gas. At this time, the test gas will not flow.

[0039] 4) Open gas path 3 and close the other gas paths. Test the amount of test gas in the carrier gas and use it as the zero point for calculation.

[0040] 5) Open gas path 1 and gas path 2, close the other gas paths, and measure the content of test gas in the carrier gas to calculate the gas permeation of the membrane under test.

[0041] Before starting the above steps, you can turn on each temperature control device to preheat the temperature to the required test temperature.

[0042] After the gas collection is completed, the quantitative loop is passed into the gas chromatograph for testing. The gas collection volume of the quantitative loop is 5 mL.

[0043] Any techniques not mentioned in this invention are based on existing technologies.

[0044] This invention presents a device for determining gas permeability using gas chromatography. This device achieves high accuracy in gas chromatography determination of gas permeability and is applicable to various gases. It is simple and convenient to operate, requiring no special professional skills, and offers high testing efficiency. The device has a compact and reasonable structure, and its size is small and flexible. Compared with existing coulometric detectors and pressure detectors, this method provides a device for connecting to a higher-precision gas chromatograph. For products requiring higher precision detection, a gas chromatograph-mass spectrometer can be connected in series to achieve ppt-level detection accuracy. Simultaneously, the gas chromatograph can be used to determine the barrier properties of a sample to other gases, achieving multi-purpose functionality. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of an apparatus for determining gas permeability using gas chromatography.

[0046] In the diagram, 1 represents the test chamber, 101 the first support plate, 102 the second support plate, 103 the third support plate, 104 the first telescopic rod, 105 the second telescopic rod, 2 the outer casing, 201 the control circuit, 3 the test box, 301 the left box, 302 the right box, 303 the pneumatic telescopic rod, 4 the carrier gas temperature control device, 5 the test gas temperature control device, 6 the first carrier gas pipe, 7 the first test gas pipe, 8 the first molecular sieve, 9 the second molecular sieve, 10 the second carrier gas pipe, 11 the second test gas pipe, 12 the third carrier gas pipe, 13 the third test gas pipe, 14 the fourth carrier gas pipe, and 15 the fourth test gas pipe. 16 is the carrier gas inlet connection pipe, 17 is the test gas inlet connection pipe, 18 is the carrier gas outlet connection pipe, 19 is the test gas outlet connection pipe, 20 is the fifth carrier gas pipe, 21 is the fifth test gas pipe, 22 is the sixth carrier gas pipe, 23 is the metering loop, 24 is the gas chromatograph, 25 is the chamber temperature control device, 26 is the carrier gas inlet transition pipe, 27 is the test gas inlet transition pipe, 28 is the carrier gas outlet transition pipe, 29 is the first pressure gauge, 30 is the second pressure gauge, 31 is the first flow meter, 32 is the second flow meter, 33 is the inlet three-way valve, 34 is the inlet four-way valve, 35 is the outlet four-way valve, 36 is the carrier gas, 37 is the test gas, and 38 is the vent. Detailed Implementation

[0047] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0048] The directional terms used in this application, such as up and down, left and right, horizontal, and vertical, are all based on the relative orientations or positional relationships shown in the attached drawings and should not be construed as absolute limitations on this application.

[0049] Example 1

[0050] like Figure 1As shown, an apparatus for determining gas permeability by gas chromatography includes a test chamber, a shell, a test box, a carrier gas temperature control device, a test gas temperature control device, a first carrier gas tube, a first test gas tube, a first molecular sieve, a second molecular sieve, a second carrier gas tube, a second test gas tube, a third carrier gas tube, a third test gas tube, a fourth carrier gas tube, a fourth test gas tube, a carrier gas inlet connection tube, a test gas inlet connection tube, a carrier gas outlet connection tube, a test gas outlet connection tube, a fifth carrier gas tube, a fifth test gas tube, a sixth carrier gas tube, a quantitative loop, and a gas chromatograph.

[0051] The test chamber is located inside the outer shell on the right side, and the test box is located inside the test chamber. There are three identical test boxes, allowing for parallel testing of three samples simultaneously. Each test box consists of a left and a right chamber. The left chamber has a left chamber on the right side, and the right chamber has a right chamber on the left side. The left and right chambers are movably connected together (i.e., the left and right chambers are facing each other; when the test membrane is not installed, they are interconnected, forming a complete cavity). A seal is provided between the left and right chambers, with a sealing grease layer on the seal. The left and right chambers form a connected and sealed air cavity. Simultaneously, the left and right shells have interlocking anti-misalignment structures to prevent misalignment. For example, both the left and right chambers have square cross-sections. The anti-misalignment structure includes four positioning rods located at the four corners of the outer perimeter of the sealing ring on the right side of the left chamber and the right shell... Four positioning through holes are set at the four corners of the outer perimeter of the left sealing ring. The positioning rod corresponds to each positioning through hole. The height of the positioning rod is greater than the depth of the positioning through hole. The positioning rod has an elongated hole set along the axial direction. When the left and right housings are movably connected together (meaning the cavities of the two housings are facing each other), the positioning rod is inserted into the corresponding positioning through hole. The left and right sealing rings are in a compressed state, and the positioning rod extends beyond the corresponding positioning through hole. The L-shaped pin is movably inserted into the elongated hole of the corresponding positioning rod that extends beyond the positioning through hole. The bottom outer side of the left housing has a carrier gas inlet connector, and the top outer side of the left housing has a carrier gas outlet connector. Both the carrier gas inlet connector and the carrier gas outlet connector are connected to the left chamber. The bottom outer side of the right housing has a test gas inlet connector, and the top outer side of the right housing has a test gas outlet connector. Both the test gas inlet connector and the test gas outlet connector are connected to the right chamber.

[0052] The carrier gas temperature control device and the test gas temperature control device are located on the left side wall inside the outer shell. One end of the third carrier gas pipe is connected to the inlet of the carrier gas temperature control device, and the other end extends out of the side wall of the outer shell to form a carrier gas inlet. One end of the first carrier gas pipe is connected to the carrier gas source, and the other end is connected to the inlet of the first molecular sieve. One end of the second carrier gas pipe is connected to the outlet of the first molecular sieve, and the other end is connected to the carrier gas inlet. One end of the fourth carrier gas pipe is connected to the outlet of the carrier gas temperature control device, and the other end is connected to the inlet of the carrier gas inlet connecting pipe. The carrier gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet branches of the carrier gas inlet connecting pipe are two or more carrier gas inlet branch pipes. The number of carrier gas inlet branch pipes is equal to the number of test chambers and corresponds one-to-one. The carrier gas inlet branch pipes extend into the test chamber and are connected to the carrier gas inlet connector on the corresponding test chamber.

[0053] The third test gas tube connects to the inlet of the test gas temperature control device at one end and extends through the side wall of the outer shell to form a test gas inlet at the other end. The first test gas tube connects to the test gas source at one end and to the inlet of the second molecular sieve at the other end. The second test gas tube connects to the outlet of the second molecular sieve at one end and to the test gas inlet at the other end. The fourth test gas tube connects to the outlet of the test gas temperature control device at one end and to the inlet of the test gas inlet connecting pipe at the other end. The test gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet branches of the test gas inlet connecting pipe are two or more test gas inlet branch pipes. The number of test gas inlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas inlet branch pipes extend into the test chamber and are connected to the test gas inlet connector on their corresponding test boxes.

[0054] Both the carrier gas outlet connection pipe and the test gas outlet connection pipe are installed on the top of the test chamber. The inlet branches of the carrier gas outlet connection pipe are two or more carrier gas outlet branch pipes. The number of carrier gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The carrier gas outlet branch pipes extend into the test chamber and are connected to the carrier gas outlet connector on their corresponding test boxes. The inlet branches of the test gas outlet connection pipe are two or more test gas outlet branch pipes. The number of test gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas outlet branch pipes extend into the test chamber and are connected to the test gas outlet connector on their corresponding test boxes.

[0055] One end of the fifth carrier gas tube is connected to the outlet of the carrier gas outlet connection tube, and the other end extends through the side wall of the outer shell to branch into a carrier gas venting tube and a carrier gas test tube; one end of the fifth test gas tube is connected to the outlet of the test gas outlet connection tube, and the other end extends through the side wall of the outer shell to form a test venting tube.

[0056] One end of the sixth carrier gas tube is connected to the fourth carrier gas tube, and the other end is connected to the fifth carrier gas tube; the carrier gas test tube, quantitative loop and gas chromatograph are connected in sequence through pipelines; an inspection window is provided on the outer shell, and the inspection window is sealed with a movable inspection door.

[0057] Example 2

[0058] Based on Embodiment 1, the following improvements were made: To simplify the equipment and facilitate assembly, the test chamber includes a first support plate, a second support plate, and a third support plate. The first support plate is installed at the bottom of the test chamber via a first telescopic rod; the third support plate is pressed against the side wall of the test chamber, and the second support plate is installed on the third support plate via a second telescopic rod. The first and second support plates are parallel and opposite to each other, and the space between the first and second support plates forms the test chamber. The distance between the first and second support plates can be adjusted by extending and retracting the first and / or second telescopic rods, thereby enabling the disassembly and assembly of the test chamber. An entrance / exit is provided on the outer shell facing the test chamber, and a sealing door is movably connected to the entrance / exit to facilitate the removal and installation of the test chamber. To improve the stability of use, the carrier gas inlet connection pipe, the test gas inlet connection pipe, the carrier gas outlet connection pipe, and the test gas outlet connection pipe are all copper pipes; the carrier gas inlet connection pipe and the test gas inlet connection pipe are welded to the first support plate, and the carrier gas outlet connection pipe and the test gas outlet connection pipe are welded to the second support plate. Figure 1 The solid line represents the test box being pulled out, while the dashed line represents the test box being positioned inside the test chamber. Figure 1 The test box is designed with an outward-pulling structure, similar to a drawer, which makes it convenient to use.

[0059] Example 3

[0060] Based on Example 2, the following improvements were made: To improve airtightness and facilitate operation, pneumatic telescopic rods were installed on the left side of the left chamber and the right side of the right chamber of the test chamber for clamping the sample. The anti-misalignment structure includes positioning rods on the periphery of the right side of the left chamber, positioning through holes and pins on the periphery of the left side of the right chamber. There are four positioning rods and four positioning through holes, which correspond one-to-one. The outer diameter of the two positioning rods and the inner diameter of the two positioning through holes at the top are larger than the outer diameter of the two positioning rods and the inner diameter of the two positioning through holes at the bottom. There are four positioning rods and four positioning through holes, with two located at the top two corners and two located at the bottom two corners. The thickness of the positioning rods and positioning through holes at the top and bottom are set to be different, so that only the positioning rods at the top can be inserted into the top. The bottom positioning rod cannot be inserted into the top through hole. If the left or right housing is inverted, they cannot be connected. The height of the positioning rod is greater than the depth of the positioning through hole. The positioning rod has an axially oriented elongated hole. When the left and right housings are connected in opposite directions, the seal between them (with a sealing grease layer) is compressed. The positioning rod is inserted into the corresponding positioning through hole and extends beyond it. The pin is inserted into the elongated hole of the corresponding positioning rod extending beyond the positioning through hole. After the pin is inserted, the left and right sealing rings remain compressed, preventing misalignment and providing effective fixation. The elongated hole on the pin does not affect the clamping of the pneumatic telescopic rod on the left and right housings. To improve the temperature uniformity inside the housing and thus the accuracy of the test, a cavity temperature control device is provided at the bottom left and top right of the housing. The control circuit is located on the top left side of the housing to control the temperature inside the housing. The cavity temperature control device, carrier gas temperature control device, and test gas temperature control device are all connected to the control circuit. The structure and connection method of the control circuit adopt mature existing technologies.

[0061] Example 4

[0062] Based on Example 3, the following improvements were made: To facilitate disassembly, assembly, handling, and storage, the apparatus for determining gas permeability by gas chromatography further includes a carrier gas inlet transition tube, a test gas inlet transition tube, and a carrier gas outlet transition tube. The two ends of the carrier gas inlet transition tube are connected to the carrier gas inlet and the second carrier gas tube via quick-connect structures, and a first pressure gauge is installed on the carrier gas inlet transition tube. The two ends of the test gas inlet transition tube are connected to the test gas inlet and the second test gas tube via quick-connect structures, and a second pressure gauge is installed on the test gas inlet transition tube. The two ends of the carrier gas outlet transition tube are connected to the metering ring and the carrier gas test tube via quick-connect structures. The quick-connect structure is a connection port that allows for quick insertion and removal, facilitating rapid disassembly and assembly. For ease of maintenance, the two ends of the fourth carrier gas tube are connected to the outlet of the carrier gas temperature control device and the inlet of the carrier gas inlet connection tube via quick-connect structures, and a first flow meter is installed on the fourth carrier gas tube. The two ends of the fourth test gas tube are connected to the outlet of the test gas temperature control device and the inlet of the test gas inlet connection tube via quick-connect structures, and a second flow meter is installed on the fourth test gas tube. This facilitates quick disassembly, assembly, inspection, and maintenance.

[0063] Example 5

[0064] Based on Example 4, the following improvements were made: For ease of control, an inlet three-way valve was provided on the fourth test gas tube, an inlet four-way valve was provided on the fourth carrier gas tube, and an outlet four-way valve was provided on the fifth carrier gas tube; the three connecting ports on the inlet three-way valve were defined as the first connecting port A, the second connecting port A, and the third connecting port A, respectively; the four connecting ports on the inlet four-way valve were defined as the first connecting port B, the second connecting port B, the third connecting port B, and the fourth connecting port B, respectively; the four connecting ports on the outlet four-way valve were defined as the first connecting port C, the second connecting port C, the third connecting port C, and the fourth connecting port C, respectively; the first connecting port A and the second connecting port A were connected to the fourth test gas tubes on both sides, respectively; the third connecting port A was connected to the first connecting port B through a pipeline; the second connecting port B and the third connecting port B were connected to the fourth carrier gas tubes on both sides, respectively; the two ends of the sixth carrier gas tube were connected to the fourth connecting port B and the first connecting port C, respectively; the second connecting port C and the third connecting port C were connected to the fifth carrier gas tubes and the carrier gas test tube on both sides, respectively; and the fourth connecting port C was connected to the carrier gas venting pipe. This allows for the creation of the required air path by controlling the valves, resulting in a simple structure and convenient use.

[0065] The apparatus described above for determining gas permeability by gas chromatography can form the following gas path:

[0066] Gas path 1: The test gas flows sequentially through the second molecular sieve, the second pressure gauge, the test gas temperature control device, the second flow meter, and the right chamber before being vented.

[0067] Gas path 2: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, the left chamber and the metering loop, and then enters the gas chromatograph;

[0068] Gas path 3: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device and the metering loop before entering the gas chromatograph;

[0069] Gas path 4: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter and the left chamber, and then is vented.

[0070] Gas path 5: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, and the right chamber before being vented.

[0071] Gas path 1 and gas path 2 are the flow directions of the test gas and the carrier gas during testing. Gas path 2 is used to measure the content of the test gas in the carrier gas and to calculate the gas permeation rate.

[0072] Gas path 3 contains the amount of test gas in the carrier gas, which serves as the zero point for calculation;

[0073] Gas path 4 is used to purge the left chamber with carrier gas before testing, and gas path 5 is used to purge the right chamber with carrier gas before testing. At this time, the test gas does not flow.

[0074] When the above-mentioned apparatus for determining gas permeability by gas chromatography is used to test the gas permeability of the membrane under test, the test method includes the following steps:

[0075] 1) Place the membrane to be tested between the left and right chambers, and connect the left and right chambers together. The membrane to be tested is placed in the left chamber on one side and the right chamber on the other side. Then, put the test box with the membrane to be tested into the test chamber and connect the corresponding pipeline.

[0076] 2) Open air passage 4, close the other air passages, and purge the left chamber with carrier gas;

[0077] 3) Open gas path 5 and close the other gas paths. Purge the right chamber with carrier gas. At this time, the test gas will not flow.

[0078] 4) Open gas path 3 and close the other gas paths. Test the amount of test gas in the carrier gas and use it as the zero point for calculation.

[0079] 5) Open gas path 1 and gas path 2, close the other gas paths, and measure the content of test gas in the carrier gas to calculate the gas permeation of the membrane under test.

[0080] Before starting the above steps, turn on all temperature control devices to preheat the temperature to the required test temperature. After collecting the gas, the quantitative loop is introduced into the gas chromatograph for testing. The gas collection volume of the quantitative loop is 5 mL.

[0081] During testing, the pressure of the first and second pressure gauges was 0.4 MPa, and the pressure of the test gas and the carrier gas were the same. The flow rate of the first and second flow meters was 10 mL / min. The temperature control devices were adjusted to maintain the temperature of the casing, the carrier gas, and the test gas at 23°C. In this example, the membrane to be tested was an aluminum-plastic composite membrane, the carrier gas was nitrogen, the test gas was oxygen, the gas chromatograph was a 7890B, and the test result was 0.01647 cm³ / m²·24h·0.1 MPa. The standard membrane was 0.01635 cm³ / m²·24h·0.1 MPa, and the deviation from the standard membrane was 0.7%.

[0082] Comparative Example

[0083] The test film was the same as in Example 5, except that an OX2 / 230 coulomb detector was used, yielding a result of 0.01796 cm³ / m²·24h·0.1 MPa with a deviation of 9.8%. A VAC-V1 differential pressure detector was used, yielding a result of 0.261 cm³ / m²·24h·0.1 MPa with a deviation of 59.6%.

[0084] Example 6

[0085] Unlike Example 5, the membrane to be tested was an aluminum-plastic composite membrane, the carrier gas was nitrogen, and the test gas was carbon dioxide. The test result was 0.04033 cm³ / m²·24h·0.1 MPa, while the standard membrane was 0.04001 cm³ / m²·24h·0.1 MPa, with a deviation of 0.8% from the standard membrane.

Claims

1. An apparatus for determining gas permeability by gas chromatography, characterized in that: It includes a test chamber, an outer shell, a test box, a carrier gas temperature control device, a test gas temperature control device, a first carrier gas tube, a first test gas tube, a first molecular sieve, a second molecular sieve, a second carrier gas tube, a second test gas tube, a third carrier gas tube, a third test gas tube, a fourth carrier gas tube, a fourth test gas tube, a carrier gas inlet connection tube, a test gas inlet connection tube, a carrier gas outlet connection tube, a test gas outlet connection tube, a fifth carrier gas tube, a fifth test gas tube, a sixth carrier gas tube, a quantitative loop, and a gas chromatograph; The test chamber is located inside the outer shell on the right side, and the test box is located inside the test chamber. There are two or more test boxes with the same structure. The test box includes a left box and a right box. The left box has a left chamber on the right side, and the right box has a right chamber on the left side. The left and right box chambers are movably connected together facing each other. There is a seal between the left and right box. The left and right chambers are spliced ​​together to form a connected and sealed air cavity. The bottom outer side of the left box has a carrier gas inlet connector, and the top outer side of the left box has a carrier gas outlet connector. The bottom outer side of the right box has a test gas inlet connector, and the top outer side of the right box has a test gas outlet connector. The left and right box are equipped with interlocking anti-misalignment structures. The carrier gas temperature control device and the test gas temperature control device are located on the left side wall inside the outer shell. One end of the third carrier gas pipe is connected to the inlet of the carrier gas temperature control device, and the other end extends out of the side wall of the outer shell to form a carrier gas inlet. One end of the first carrier gas pipe is connected to the carrier gas source, and the other end is connected to the inlet of the first molecular sieve. One end of the second carrier gas pipe is connected to the outlet of the first molecular sieve, and the other end is connected to the carrier gas inlet. One end of the fourth carrier gas pipe is connected to the outlet of the carrier gas temperature control device, and the other end is connected to the inlet of the carrier gas inlet connecting pipe. The carrier gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet branches of the carrier gas inlet connecting pipe are two or more carrier gas inlet branch pipes. The number of carrier gas inlet branch pipes is equal to the number of test chambers and corresponds one-to-one. The carrier gas inlet branch pipes extend into the test chamber and are connected to the carrier gas inlet connector on the corresponding test chamber. The third test gas tube is connected to the inlet of the test gas temperature control device at one end and extends through the side wall of the outer shell to form a test gas inlet at the other end. The first test gas tube is connected to the test gas source at one end and to the inlet of the second molecular sieve at the other end. The second test gas tube is connected to the outlet of the second molecular sieve at one end and to the test gas inlet at the other end. The fourth test gas pipe is connected at one end to the outlet of the test gas temperature control device and at the other end to the inlet of the test gas inlet connecting pipe. The test gas inlet connecting pipe is installed at the bottom of the test chamber. The outlet of the test gas inlet connecting pipe is branched into two or more test gas inlet branch pipes. The number of test gas inlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas inlet branch pipe extends into the test chamber and is connected to the test gas inlet connector on its corresponding test box. Both the carrier gas outlet connection pipe and the test gas outlet connection pipe are installed on the top of the test chamber. The inlet branches of the carrier gas outlet connection pipe are two or more carrier gas outlet branch pipes. The number of carrier gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The carrier gas outlet branch pipes extend into the test chamber and are connected to the carrier gas outlet connector on their corresponding test boxes. The inlet branches of the test gas outlet connection pipe are two or more test gas outlet branch pipes. The number of test gas outlet branch pipes is equal to the number of test boxes and corresponds one-to-one. The test gas outlet branch pipes extend into the test chamber and are connected to the test gas outlet connector on their corresponding test boxes. One end of the fifth carrier gas tube is connected to the outlet of the carrier gas outlet connection tube, and the other end extends out of the side wall of the outer shell and branches into the carrier gas venting tube and the carrier gas test tube. The fifth test air tube is connected at one end to the outlet of the test air outlet connection tube, and the other end extends through the side wall of the outer shell to form a test air vent tube; One end of the sixth carrier tube is connected to the fourth carrier tube, and the other end is connected to the fifth carrier tube; The carrier gas test tube, quantitative loop, and gas chromatograph are connected in sequence via tubing.

2. The apparatus for determining gas permeability by gas chromatography as described in claim 1, characterized in that: The test chamber includes a first support plate, a second support plate, and a third support plate. The first support plate is installed at the bottom of the test chamber via a first telescopic rod. The third support plate is pressed against the side wall of the test chamber. The second support plate is installed on the third support plate via a second telescopic rod. The first and second support plates are parallel and opposite to each other, and the space between the first and second support plates forms the test chamber. The distance between the first and second support plates can be adjusted by extending and retracting the first and / or second telescopic rods, thereby enabling the assembly and disassembly of the test chamber. An entrance / exit is provided on the outer shell facing the test chamber, and a sealed door is movably connected to the entrance / exit.

3. The apparatus for determining gas permeability by gas chromatography as described in claim 2, characterized in that: The carrier gas inlet connection pipe, the test inlet connection pipe, the carrier gas outlet connection pipe, and the test outlet connection pipe are all copper pipes; the carrier gas inlet connection pipe and the test inlet connection pipe are welded to the first support plate, and the carrier gas outlet connection pipe and the test outlet connection pipe are welded to the second support plate.

4. The apparatus for determining gas permeability by gas chromatography as described in any one of claims 1-3, characterized in that: The test chamber has pneumatic telescopic rods on the left side of the left chamber and the right side of the right chamber. The anti-misalignment structure includes at least two positioning rods on the periphery of the right side of the left chamber, at least two positioning through holes and a pin on the periphery of the left side of the right chamber. The number of positioning rods is equal to the number of positioning through holes and they correspond one-to-one. The height of the positioning rod is greater than the depth of the positioning through hole. The positioning rod has an elongated hole arranged along the axial direction. When the left and right chambers are movably connected together, the seal between the left and right chambers is under compression. The positioning rod is movably inserted into the corresponding positioning through hole and extends beyond the corresponding positioning through hole. The pin is movably inserted into the elongated hole of the corresponding positioning rod that extends beyond the positioning through hole.

5. The apparatus for determining gas permeability by gas chromatography as described in any one of claims 1-3, characterized in that: Temperature control devices are located on the bottom left and top right sides of the outer casing.

6. The apparatus for determining gas permeability by gas chromatography as described in any one of claims 1-3, characterized in that: It also includes a carrier gas inlet transition tube, a test gas inlet transition tube, and a carrier gas outlet transition tube; the two ends of the carrier gas inlet transition tube are respectively connected to the carrier gas inlet and the second carrier gas tube via quick-connect structures, and a first pressure gauge is provided on the carrier gas inlet transition tube; the two ends of the test gas inlet transition tube are respectively connected to the test gas inlet and the second test gas tube via quick-connect structures, and a second pressure gauge is provided on the test gas inlet transition tube; the two ends of the carrier gas outlet transition tube are respectively connected to the metering ring and the carrier gas test tube via quick-connect structures.

7. The apparatus for determining gas permeability by gas chromatography as described in claim 6, characterized in that: The two ends of the fourth carrier gas pipe are connected to the outlet of the carrier gas temperature control device and the inlet of the carrier gas inlet connecting pipe via quick-connect structures, and the fourth carrier gas pipe is equipped with a first flow meter; the two ends of the fourth test gas pipe are connected to the outlet of the test gas temperature control device and the inlet of the test gas inlet connecting pipe via quick-connect structures, and the fourth test gas pipe is equipped with a second flow meter.

8. The apparatus for determining gas permeability by gas chromatography as described in claim 7, characterized in that: The fourth test air tube is equipped with an inlet three-way valve, the fourth carrier air tube is equipped with an inlet four-way valve, and the fifth carrier air tube is equipped with an outlet four-way valve. The three ports on the inlet three-way valve are defined as the first port A, the second port A, and the third port A, respectively. The four ports on the inlet four-way valve are defined as the first port B, the second port B, the third port B, and the fourth port B, respectively. The four ports on the outlet four-way valve are defined as the first port C, the second port C, the third port C, and the fourth port C, respectively. The first port A and the second port A are connected to the fourth test air tubes on both sides, the third port A is connected to the first port B through a pipeline, the second port B and the third port B are connected to the fourth carrier air tubes on both sides, the two ends of the sixth carrier air tube are connected to the fourth port B and the first port C, the second port C and the third port C are connected to the fifth carrier air tubes and the carrier air test tube on both sides, respectively, and the fourth port C is connected to the carrier air venting pipe.

9. The apparatus for determining gas permeability by gas chromatography as described in claim 8, characterized in that: The following airflow path is formed: Gas path 1: The test gas flows sequentially through the second molecular sieve, the second pressure gauge, the test gas temperature control device, the second flow meter, and the right chamber before being vented. Gas path 2: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, the left chamber and the metering loop, and then enters the gas chromatograph; Gas path 3: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device and the metering loop before entering the gas chromatograph; Gas path 4: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter and the left chamber, and then is vented. Gas path 5: The carrier gas flows sequentially through the first molecular sieve, the first pressure gauge, the carrier gas temperature control device, the first flow meter, and the right chamber before being emptied. Gas path 1 and gas path 2 are the flow directions of the test gas and the carrier gas during testing. Gas path 2 is used to measure the content of the test gas in the carrier gas and to calculate the gas permeation rate. Gas path 3 contains the amount of test gas in the carrier gas, which serves as the zero point for calculation; Gas path 4 is used to purge the left chamber with carrier gas before testing, and gas path 5 is used to purge the right chamber with carrier gas before testing. At this time, the test gas does not flow.

10. The apparatus for determining gas permeability by gas chromatography as described in claim 9, characterized in that: The method for determining the gas permeability of a membrane under test includes the following steps: 1) Place the membrane to be tested between the left and right chambers, and connect the left and right chambers together. The membrane to be tested is placed in the left chamber on one side and the right chamber on the other side. Then, put the test box with the membrane to be tested into the test chamber and connect the corresponding pipeline. 2) Open air passage 4, close the other air passages, and purge the left chamber with carrier gas; 3) Open gas path 5 and close the other gas paths. Purge the right chamber with carrier gas. At this time, the test gas will not flow. 4) Open gas path 3 and close the other gas paths. Test the amount of test gas in the carrier gas and use it as the zero point for calculation. 5) Open gas path 1 and gas path 2, close the other gas paths, and measure the content of test gas in the carrier gas to calculate the gas permeation of the membrane under test.

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