Double-flow-path gas chromatography device, analysis method and application

Abstract

The invention relates to the technical field of new energy and energy conservation, and particularly discloses a double-flow-path gas chromatography device, an analysis method and application. The device comprises a sample injection system, a carrier gas purification system, a low-temperature concentration system, a chromatographic detection system, a switching device and the like, the carrier gas purification system is connected with the low-temperature concentration system and the chromatographic detection system, the switching device is adopted for switching flow paths, and trace impurities in high-purity gas can be detected at high sensitivity through multi-stage carrier gas purification and distribution, double-flow path physical isolation and low-temperature concentration and enrichment. Meanwhile, a double-flow-path parallel analysis method is provided, when a current sample is subjected to chromatographic detection, a low-temperature concentration system can synchronously enrich a next sample, and the efficiency is improved. The device is provided with a bypass analysis system, so that free switching of constant / microanalysis is realized. Aiming at the multi-point continuous monitoring of the hydrogen liquefaction system, a multi-path sample injection switching system is arranged, the sample injection detection is automatically switched on line, the manual error is avoided, the efficiency is improved, the analysis mode switching can be realized, and the flexibility is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of new energy and energy-saving technology, and specifically relates to a dual-flow path gas chromatography device, an analysis method and an application thereof. Background Art

[0002] With the growing global demand for clean energy, hydrogen, as a highly promising energy carrier, is playing an increasingly important role in the energy sector. With significant advantages such as high combustion calorific value and pollution-free products, it is widely used in a variety of fields, including fuel cell vehicles, distributed power generation, and energy storage. However, the purity of hydrogen has a crucial impact on its application performance and safety. In hydrogen liquefaction systems, in particular, large-scale hydrogen liquefaction systems are one of the key infrastructures of the hydrogen energy industry. Hydrogen analysis systems are an essential component of equipment commissioning and daily operations. Their analysis results can intuitively reflect equipment operation, verify gas source purity, the gas-liquid state during the process, and the composition of the product.

[0003] Currently, gas chromatography has become one of the most widely used technologies for hydrogen impurity analysis due to its advantages such as high separation efficiency, high detection sensitivity, and relatively fast analysis speed. However, due to factors such as limited offline sample volume and single-flow configuration, existing gas chromatography can only perform routine analysis of gases with impurity concentrations above 100 ppm. Its sensitivity for detecting trace impurities is limited, making it difficult to meet the detection requirements of hydrogen liquefaction systems that require hydrogen impurity levels to be controlled below tens of ppm during cryogenic processes.

[0004] Furthermore, as hydrogen liquefaction systems grow in scale, the number of analytical points required increases. Traditional offline sampling and analysis methods are no longer able to meet the requirements for continuous, automated system operation. Due to the high precision of analytical equipment, manual offline sampling inevitably leads to biased or invalid results due to human factors such as contamination during the sampling process and improper sampling timing. Therefore, the need for online, continuously automated switching analytical equipment has become essential.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The first purpose of the present invention is to provide a dual-flow gas chromatography device to address the problems of insufficient detection capability of existing gas chromatography technology for trace impurities below 100 ppm and susceptibility to residual contamination of single-flow design. Through multi-stage carrier gas purification and diversion, dual-flow physical isolation, and low-temperature concentration and enrichment, high-sensitivity detection of trace impurities (such as oxygen, nitrogen, etc.) in high-purity gas is achieved.

[0007] The second purpose of the present invention is to address the problem of low efficiency of traditional single-flow gas chromatography analysis. By setting a switching device in a dual-flow gas chromatography device, dual-flow parallel analysis can be achieved. When the chromatographic detection system analyzes the current sample, the low-temperature concentration system synchronously enriches the next sample, providing a method that can shorten the analysis cycle and improve analysis efficiency.

[0008] A third object of the present invention is to address the problem that existing technologies are not compatible with impurity detection in different concentration ranges. By setting up a bypass analysis system and a switching device, an analysis method that can freely switch between constant analysis (several hundred to several thousand ppm) and trace analysis (0.1-150 ppm) is provided.

[0009] The fourth purpose of the present invention is to address the problems that multiple analysis points in the hydrogen liquefaction system need to be continuously monitored, manual sampling is prone to contamination and low efficiency. By setting a multi-channel injection switching system in a dual-flow gas chromatography device, online automatic switching injection and detection of samples at different points can be achieved, thereby avoiding manual operation errors and improving analysis efficiency; at the same time, the bypass analysis system and dual-flow parallel analysis method of the dual-flow gas chromatography device are used to realize free switching of trace / constant analysis mode, further improving analysis efficiency and flexibility.

[0010] To achieve at least one of the above-mentioned invention objectives, the technical solution of the present invention is as follows:

[0011] The present invention provides a dual-flow path gas chromatography device, comprising:

[0012] Carrier gas purification system, used for purifying the carrier gas;

[0013] a cryogenic concentration system connected to an output end of the carrier gas purification system;

[0014] a chromatographic detection system connected to the output end of the carrier gas purification system and arranged in parallel with the cryogenic concentration system;

[0015] a switching device for transferring the sample enriched by the cryogenic concentration system to the chromatographic detection system;

[0016] Sample introduction system for delivering external samples to the cryoconcentration system.

[0017] The dual-flow path gas chromatography device provided by the present invention adopts a dual-flow path physical isolation design, that is, the carrier gas purification system shunts the carrier gas after purification, and provides carrier gas for the low-temperature concentration system and the chromatographic detection system respectively. At the same time, the switching device is connected to the low-temperature concentration system and the chromatographic detection system respectively, so as to transfer the sample enriched by the low-temperature concentration system to the chromatographic detection system, forming two independent flow paths (concentration flow path and detection flow path), realizing physical isolation of the concentration flow path (responsible for sample enrichment) and the detection flow path (responsible for separation and detection), which do not affect each other during operation, avoid contamination of subsequent detection by concentrated residual impurities in the traditional single flow path, and improve the analysis speed and stability of the system. For example, the main gas is directly emptied during the concentration process, and the detection flow path is connected to the concentration column only at the moment of injection, which greatly reduces the risk of cross contamination.

[0018] In the above technical solution, the switching time of the switching device is ≤ 0.5 seconds;

[0019] Optionally, the switching device is a six-way valve, and the flow path switching between the low-temperature concentration system and the chromatographic detection system is achieved by switching the position of the six-way valve.

[0020] The switching device can not only connect the low-temperature concentration system and the chromatographic detection system, but also the carrier gas purification system, that is, the switching device can control the flow direction and on-off of the carrier gas in the concentration flow path and the detection flow path. At this time, the switching device switches ultra-fast to avoid flow interruption in the detection flow path, so that the working state of the thermal conductivity detector is not affected by changes in the carrier gas, and solves the problem of sudden baseline changes caused by single flow path switching, thereby increasing the analysis speed of the instrument by more than 2 times that of the hydrogen analyzer using a series single gas path, improving analysis efficiency and baseline stability.

[0021] In the above technical solution, the carrier gas purification system includes a carrier gas source and a purification unit connected in sequence through a pipeline, and the outlet end of the purification unit serves as the output end of the carrier gas purification system;

[0022] Optionally, the purification unit includes at least two stages of purification units;

[0023] Optionally, the purification unit includes a first-stage purification unit and a second-stage purification unit connected in sequence through a pipeline;

[0024] Optionally, the first-stage purification unit is a silica gel-5A molecular sieve room temperature adsorption tube, and the second-stage purification unit is a 5A molecular sieve low-temperature adsorption tube;

[0025] Optionally, a pressure reducing table is provided between the carrier gas source and the purification unit.

[0026] Silica gel is used as a desiccant due to its excellent hygroscopic properties. Silica gel-5A molecular sieve is used as the first-stage crude adsorption at room temperature to effectively remove most of the residual moisture and remove some oxygen, carbon dioxide and organic vapor. After the first-stage crude adsorption is completed, 5A molecular sieve can give full play to its stronger ability to adsorb oxygen, carbon dioxide and organic vapor impurities at low temperature, so it is used as the second-stage adsorption. The carrier gas is purified by the silica gel-5A molecular sieve room temperature adsorption tube and the 5A molecular sieve low temperature purification tube to remove impurities such as oxygen, nitrogen, and water vapor, thereby reducing the detection baseline noise from the source, avoiding the interference of carrier gas impurities on trace sample signals, and ensuring the accuracy of the detection results. The silica gel-5A molecular sieve room temperature adsorption tube (3) and the 5A molecular sieve low temperature purification tube (4) are connected by a stainless steel tube, and the connection part is sealed with a conical gasket. Through the above improvements, the baseline drift within 30 minutes is reduced from about 100uV to less than 30uV.

[0027] A gas flow control device, such as a spring-loaded gas resistor, can be installed on the pipeline connecting the output end of the carrier gas purification system and the cryogenic concentration system. The spring-loaded gas resistor can reduce the high-pressure carrier gas (e.g., 0.35 MPa) to a low pressure (below 0.1 MPa) and stabilize the flow rate at 300-800 mL / min. This meets the cryogenic concentration system's concentration column's requirement for high-flow, low-pressure carrier gas, ensures that the sample gas and carrier gas are fully mixed in the concentration column, and improves the adsorption efficiency of trace impurities (such as oxygen and nitrogen).

[0028] Gas flow control devices, such as a pressure-stabilizing valve, a pressure gauge, and a needle valve, can be installed on the pipeline connecting the output end of the carrier gas purification system and the chromatographic detection system. The pressure-stabilizing valve stabilizes the carrier gas pressure of the chromatographic detection system (such as 0.35 MPa) to prevent gas source pressure fluctuations from affecting the detection baseline; a pressure gauge is set to monitor the carrier gas pressure in real time; and a needle valve is set to adjust the carrier gas flow rate (20-50 mL / min) to meet the flow rate requirements of different chromatographic columns.

[0029] In the above technical solution, the low-temperature concentration system includes a concentration column and a fixed volume sampling device that are connected to each other;

[0030] The inlet end of the concentrating column is connected to the output end of the carrier gas purification system;

[0031] The fixed volume sampling device is connected to the switching device;

[0032] Optionally, the fixed volume sampling device is a fixed volume sampling valve, which introduces the enriched sample into the chromatographic detection system through a switching device;

[0033] Optionally, the low-temperature concentration system further comprises a bubbler and a wet flow meter connected in sequence via pipelines, and the inlet end of the bubbler is connected to the output end of the carrier gas purification system and / or the outlet end of the concentration column.

[0034] The concentrator column significantly enhances its adsorption capacity for target impurities (such as oxygen and nitrogen) in a low-temperature environment (e.g., liquid neon cooling). The primary gas (e.g., hydrogen) is exhausted through a bubbler and wet flowmeter, achieving efficient enrichment of trace impurities (the injection volume can be increased from the conventional 2mL to 400mL, with an enrichment factor of ≥200 times). This solves the problem of traditional gas chromatography that prevents detection of trace impurities (<10ppm) due to insufficient injection volume. A fixed-volume sampling valve is connected to the inlet and outlet of the concentrator column to accurately intercept the enriched sample and introduce it into the chromatographic detection system, avoiding the volume error of manual injection and improving the repeatability and reliability of trace analysis.

[0035] In the above technical solution, the chromatographic detection system includes a vaporization chamber, a chromatographic column, and a thermal conductivity cell connected in sequence through pipelines, and the inlet end of the vaporization chamber is connected to the switching device and the output end of the carrier gas purification system.

[0036] The present invention uses a stable thermal conductivity cell detector for analysis and detection. The carrier gas undergoes multi-stage purification, and the carrier gas used in the detection system does not pass through a cryogenic concentration system, thus avoiding impurity residue and cross-contamination, resulting in a very stable instrument baseline. The baseline remains virtually unchanged when the millivolt recorder is operated continuously for 20 hours. This stable baseline ensures accurate and reproducible analytical data and demonstrates the instrument's excellent sealing performance.

[0037] The dual-flow path gas chromatography device structure provided by the present invention is suitable for a variety of gas matrices (such as hydrogen, helium, and nitrogen) and target impurities (oxygen, nitrogen, and carbon dioxide, etc.). It can be flexibly adapted to different detection needs by replacing the material of the carrier gas purification unit, the concentration column, the chromatographic column filler, or adjusting the concentration temperature.

[0038] In the above technical solution, the dual-flow gas chromatography device also includes a bypass analysis system, which includes:

[0039] The bypass pipe has an air inlet connected to the output of the carrier gas purification system and an air outlet connected to the thermal conductivity cell of the chromatographic detection system. The bypass pipe is provided with the following components in sequence along the direction of carrier gas flow:

[0040] Bypass pressure gauge, used to monitor carrier gas pressure;

[0041] A connecting tube, wherein a bypass injection device is installed on the connecting tube,

[0042] a bypass vaporization chamber connected to the downstream end of the connecting pipe through a bypass pipe;

[0043] A bypass chromatographic column, one end of which is connected to the bypass vaporization chamber, and the other end of which is connected to a thermal conductivity cell detector (20);

[0044] Optionally, the bypass sampling device includes a bypass six-way valve and a quantitative tube connected to each other, wherein the six-way valve is used to control the sample to enter the bypass pipeline through the quantitative tube, pass through the bypass vaporization chamber and the bypass chromatographic column, and then be detected by the thermal conductivity cell detector (20).

[0045] In engineering, a bypass analysis system is added to the dual-flow gas chromatography device, which can not only be used specifically for constant analysis, but also serve as a backup in case of sudden failure of the main chromatography detection system, such as chromatographic column rupture.

[0046] The above technical solution further includes a multi-channel injection switching system, which is connected to the sample injection system, and the multi-channel injection switching system includes:

[0047] Multiple injection branches, one end of each injection branch is used to connect to a different external sample source; the other end is connected to the sample injection system;

[0048] Multiple solenoid valves, each of which is installed on a corresponding sampling branch pipe to control the on / off of the sampling branch pipe;

[0049] A control system is electrically connected to the multiple solenoid valves and is used to automatically switch the solenoid valves on and off according to a preset timing to achieve online continuous sampling of different external sample sources.

[0050] The present invention also provides an analysis method for gas impurity analysis using the dual-flow-path gas chromatography apparatus, comprising the following steps:

[0051] Carrier gas purification and diversion: After being purified by the carrier gas purification system, the carrier gas is diverted to provide carrier gas for the cryogenic concentration system and the chromatographic detection system respectively;

[0052] Sample concentration: The external sample enters the cryogenic concentration system through the sample injection system, and the target impurities are enriched at low temperature, and the main gas is exhausted;

[0053] Sample injection switching: operating the switching device to allow the sample enriched with impurities to enter the chromatographic detection system through the switching device;

[0054] Separation and detection: The sample is vaporized, separated and detected in the chromatographic detection system to obtain the target impurity analysis results.

[0055] The dual-flow path gas chromatography device provided by the present invention adopts a dual-flow path physical isolation design, that is, after the carrier gas is purified, it is split into two independent paths, which are used for the low-temperature concentration system and the chromatographic detection system respectively, to realize the analysis of trace impurities in high-purity gas. After the carrier gas is purified, it is split, and a part of the carrier gas is continuously and stably passed into the detection system to maintain a stable baseline; the other part of the carrier gas is passed into the low-temperature concentration system at a large flow rate to provide sufficient gas source for low-temperature concentration, help concentrate the sample, and ensure the effective enrichment of trace impurities. In the prior art, when detecting trace impurities in high-purity gas, concentration and detection share the same flow path, and residual samples or carrier gas impurities will contaminate the subsequent detection process, resulting in baseline drift or cross-contamination. The present invention completely separates the concentration flow path from the detection flow path, and the high-purity gas sample is enriched with impurities through a low-temperature adsorption column. At this time, the carrier gas is only used to transport the sample to the adsorption column and does not enter the detector; after the adsorption is completed, it can be transferred to an independent chromatographic detection system for analysis through a switching device, avoiding adsorption residues or carrier gas impurities interfering with the detection baseline, thereby improving sensitivity and repeatability.

[0056] In the above technical solution, while the chromatographic detection system is separating and detecting the current sample, the low-temperature concentration system is connected to the next sample through the sample injection system and simultaneously performs concentration and enrichment to achieve dual-flow parallel analysis.

[0057] The dual-flow parallel analysis method can significantly shorten the analysis cycle and improve analysis efficiency.

[0058] Optionally, the sample is high-purity hydrogen, and the target impurities are oxygen and / or nitrogen;

[0059] Optionally, the carrier gas is high-purity hydrogen, which is diverted after oxygen and nitrogen impurities are removed by the purification unit;

[0060] The dual-flow path gas chromatography device provided by the present invention has a compact structure, is firm and reliable. When both the carrier gas and the sample are high-purity hydrogen, it can not only analyze the high-purity hydrogen used as the sample gas, but also directly detect the high-purity hydrogen used as the carrier gas source, thus achieving dual-purposes in one device and being easy to use.

[0061] Optionally, during the sample concentration step, the main body of hydrogen is evacuated through a bubbler and a wet flow meter, and oxygen and nitrogen impurities are concentrated in the concentration column;

[0062] Optionally, the low temperature environment of the concentration column in the low temperature concentration system is provided by an external inert medium device. Under normal pressure conditions, the boiling point of the inert medium is lower than the boiling point of liquid nitrogen (-196°C), which can more thoroughly remove oxygen and nitrogen impurities.

[0063] Optionally, the low temperature environment of the concentration column in the low temperature concentration system is provided by an external liquid neon device, and the temperature is controlled at -245.9°C to -197°C.

[0064] Optionally, the carrier gas flow rate of the cryogenic concentration system is 300-800 mL / min and the pressure is 0.3-0.5 MPa;

[0065] Optionally, the carrier gas flow rate of the chromatographic detection system is 30-100 mL / min and the pressure is 0.2-0.3 MPa;

[0066] In the above technical solution, when constant analysis is required, the bypass analysis system is turned on, and the sample is injected through the bypass injection device on the connecting pipe. After the pressure is monitored by the bypass pressure gauge of the bypass pipe, the carrier gas carries the sample and passes through the bypass vaporization chamber and the bypass chromatographic column for separation in sequence, and is detected by the thermal conductivity cell detector to realize the switching of the micro / constant analysis mode.

[0067] The present invention also provides an application of the dual-flow path gas chromatography device and the analysis method thereof in full-process online monitoring of a hydrogen liquefaction system.

[0068] Optionally, the device is connected to multiple analysis points of the hydrogen liquefaction system through a multi-channel injection switching system, and automatically switches the injection according to a preset time sequence;

[0069] The detection data of the method is uploaded to the main control system of the hydrogen liquefaction system in real time, and is used to adjust the temperature and pressure parameters of the liquefaction process, thereby realizing the linkage between the analysis results and the process control;

[0070] Optionally, the device is connected to at least five analysis sites of the hydrogen liquefaction system via a multi-channel sample switching system;

[0071] Optionally, the preset timing is a single-channel purge time of 5-30 minutes and an analysis number of 1-5 times.

[0072] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0073] 1. Through dual-flow physical isolation and low-temperature concentration technology, the problems of residual contamination and insufficient enrichment of trace impurities in traditional single-flow are effectively solved, and high-sensitivity detection of trace impurities such as oxygen and nitrogen in high-purity gases is achieved.

[0074] 2. The dual-flow parallel analysis method enables simultaneous detection and cryogenic concentration, without waiting for the previous sample to be completed, shortening the analysis cycle. The multi-channel injection switching system enables fully automatic operation, improving analysis and detection efficiency.

[0075] 3. Through the bypass analysis system and switching unit, the constant (hundreds to thousands of ppm) and trace (0.1-150ppm) analysis modes can be freely switched, flexibly adapting to the detection of impurities in different concentration ranges and improving the versatility of the device.

[0076] 4. The multi-channel sampling switching system realizes multi-point automatic detection in complex working conditions such as hydrogen liquefaction system, avoids manual sampling errors and contamination, and links detection data with real-time process control to improve system operation safety and automation level.

[0077] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an undue limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort. In the accompanying drawings:

[0079] Figure 1 It is a schematic diagram of a dual-flow gas chromatography device;

[0080] Figure 2 It is a schematic diagram of the "sampling (Load)" position of the six-way valve (7);

[0081] Figure 3 This is a schematic diagram of the "Inject" position of the six-way valve (7);

[0082] Figure 4 It is a control flow chart of the multi-channel injection automatic switching system.

[0083] Figure numerals: 1-carrier gas source; 2-pressure reducing gauge; 3-silica gel-5A molecular sieve room temperature adsorption tube; 4-5A molecular sieve low temperature adsorption tube; 5-spring type gas resistance; 6, 8, 10-high vacuum glass piston; 7-six-way valve; 9-constant volume sampling valve; 11-concentration column; 12-bubbler; 13-wet flow meter; 14-pressure regulating valve; 15-pressure gauge; 15-1-bypass pressure gauge; 16-needle valve; 17-bypass connecting pipe; 18-vaporization chamber; 18-1-bypass vaporization chamber; 19-chromatographic column; 19-1-bypass chromatographic column; 20 thermal conductivity cell detector; 21-sample injection line; 22-high pressure needle valve.

[0084] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0085] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0086] refer to Figure 1 The dual-flow gas chromatography device provided by the present invention includes a carrier gas purification system, a low-temperature concentration system, a chromatographic detection system, a switching device, a sample injection system, a bypass analysis system, a multi-channel injection switching system ( Figure 1 (not shown), the switching device is a six-way valve (7), the sample injection system includes a sample injection pipeline (21), a high-pressure needle valve (22), each module is connected by a stainless steel pipe, the key interface is sealed with a conical gasket, and the pipes are connected at some key positions through a vacuum glass piston (6, 8, 10), and the vacuum glass piston (6, 8, 10) is a three-way piston.

[0087] The specific structure is as follows:

[0088] 1. Carrier gas purification system

[0089] The outlet of the carrier gas source (1) is connected to the inlet of the pressure reducing gauge (2), and the outlet of the pressure reducing gauge (2) is connected to the inlet of the silica gel-5A molecular sieve room temperature adsorption tube (3); the outlet of the room temperature adsorption tube (3) is connected to the inlet of the 5A molecular sieve low temperature adsorption tube (4); the output end of the 5A molecular sieve low temperature adsorption tube (4) is divided into two branches:

[0090] The first output end is connected to the inlet end of the spring-type air resistor (5), and the outlet end of the spring-type air resistor (5) is connected to the sample injection pipeline (21) and the fifth interface of the six-way valve (7) through a high vacuum glass piston (6); a high-pressure needle valve (22) is provided on the sample injection pipeline (21).

[0091] The output end of the spring-type gas resistor (5) is simultaneously connected to the inlet end of the concentration column and the fifth interface of the six-way valve, ensuring that the auxiliary carrier gas can be used for sample concentration (directly entering the concentration column) or flow path switching (connected to other units through the six-way valve).

[0092] The second output end is connected to a pressure stabilizing valve (14) and a pressure gauge (15) in sequence, and the outlet end of the pressure gauge (15) is connected to the first interface of the six-way valve (7); a needle valve (16) is provided between the pressure stabilizing valve (14) and the pressure gauge (15);

[0093] 2. Low temperature concentration system

[0094] The inlet end of the concentration column (11) is connected to the inlet end of the fixed volume sampling valve (9) and the sixth interface of the six-way valve (7) through a high vacuum glass piston (8); the outlet end of the concentration column (11) is connected to the outlet end of the fixed volume sampling valve (9) and the third interface of the six-way valve (7) through a high vacuum glass piston (10);

[0095] The inlet end of the bubbler (12) is connected to the fourth interface of the six-way valve (7), and the outlet end of the bubbler (12) is connected to the inlet end of the wet flow meter (13).

[0096] 3. Chromatographic detection system

[0097] The inlet end of the vaporization chamber (18) is connected to the second interface of the six-way valve (7), and the outlet end of the vaporization chamber (18) is connected to the chromatographic column (19) and the thermal conductivity cell (20) in sequence.

[0098] 4. Switching device

[0099] A six-way valve (7), wherein the six-way valve (7) has six interfaces, namely a first interface, a second interface, a third interface, a fourth interface, a fifth interface and a sixth interface; wherein,

[0100] The first interface is connected to the outlet of the pressure gauge (15);

[0101] The second interface is connected to the inlet end of the vaporization chamber (18);

[0102] The third interface is connected to the outlet of the fixed volume sampling valve (9) and the outlet of the concentration column (11) through a high vacuum glass piston (10);

[0103] The fourth interface is connected to the inlet end of the bubbler (12);

[0104] The fifth interface is connected to the outlet end of the spring-type air resistor (5) and the sample injection pipeline (21) through a high vacuum glass piston (6);

[0105] The sixth interface is connected to the inlet end of the fixed volume sampling valve (9) and the inlet end of the concentration column (11) through a high vacuum glass piston (8).

[0106] 5. Sample injection system

[0107] One end of the sample injection line (21) is connected to an external sample source, and the other end is connected to the outlet end of the spring-type air resistor (5) and the fifth interface of the six-way valve (7) through a high vacuum glass piston (6). A high-pressure needle valve (22) is provided on the sample injection line (21).

[0108] 6. Vacuum glass piston (6, 8, 10)

[0109] A high vacuum glass piston (6) is provided on a pipe connecting the inlet end of the concentrating column (11) and the sample injection line (21) and the first output end of the 5A molecular sieve low temperature purification tube (4), and is used to control the on-off between the concentrating column (11) and the sample injection line (21) and the 5A molecular sieve low temperature purification tube (4). When the inlet end of the concentrating column (11) is connected to the sample injection line (21), the gas sample can enter the concentrating column (11) through the high vacuum glass piston (6); when the inlet end of the concentrating column (11) is connected to the first output end of the 5A molecular sieve low temperature purification tube (4), the carrier gas can enter the concentrating column (11) through the high vacuum glass piston (6); the gas inlet source (sample gas or carrier gas) of the concentrating column (11) is controlled by the high vacuum glass piston (6) to realize the switching between the "sample injection" and "carrier gas purging" states;

[0110] A high vacuum glass piston (8) is provided on a pipeline connecting the inlet of the fixed volume sampling valve (9), the inlet of the concentration column (11), and the sixth interface of the six-way valve (7). The high vacuum glass piston (8) selects the injection path of the fixed volume sampling valve (9) (from the inlet of the concentration column or the six-way valve), and cooperates with the six-way valve to realize the path switching between sample enrichment and injection.

[0111] A high vacuum glass piston (10) is provided on a pipeline connecting the outlet of the fixed volume sampling valve (9), the outlet of the concentration column (11), and the third interface of the six-way valve (7). The high vacuum glass piston (10) controls the output path of the fixed volume sampling valve (9) (to the outlet of the concentration column or the six-way valve), ensuring that the enriched sample is accurately introduced into the detection flow path.

[0112] 7. Bypass analysis system

[0113] The bypass pipeline has an air inlet end connected to the output end of the carrier gas purification system and an air outlet end connected to the thermal conductivity cell detector (20). The bypass pipeline is provided with the following in sequence along the carrier gas flow direction:

[0114] Bypass pressure gauge (15-1), used to monitor carrier gas pressure;

[0115] A bypass connecting pipe (17) is mounted with a bypass six-way valve (not shown in the figure), and the six-way valve is connected to a quantitative tube (not shown in the figure) for sampling;

[0116] A bypass vaporization chamber (18-1) is connected to the downstream end of the bypass connecting pipe (17) through a bypass pipeline;

[0117] A bypass chromatographic column (19-1), one end of which is connected to the bypass vaporization chamber (18-1) and the other end of which is connected to the thermal conductivity cell detector (20);

[0118] The six-way valve is used to control the sample to enter the bypass pipeline through the quantitative tube, and then pass through the bypass vaporization chamber (18-1) and the bypass chromatographic column (19-1) and then be detected by the thermal conductivity cell detector (20).

[0119] 8. Multi-channel injection switching system (not shown)

[0120] The multi-channel injection switching system is connected to the sample injection pipeline (21), and the multi-channel injection switching system includes:

[0121] Multiple sampling branches, one end of each sampling branch is used to connect to a different external sample source; the other end is connected to the sample sampling pipeline (21);

[0122] Multiple solenoid valves, each of which is installed on a corresponding sampling branch pipe to control the on / off of the sampling branch pipe;

[0123] A control system is electrically connected to the multiple solenoid valves and is used to automatically switch the solenoid valves on and off according to a preset timing to achieve online continuous sampling of different external sample sources.

[0124] Example 1: Detection of trace oxygen and nitrogen impurities in high-purity hydrogen (0.1-150 ppm)

[0125] First, the six-way valve (7) switches between "Load" and "Inject" as follows:

[0126] "Sampling (Load)" bit (refer to Figure 2 ): The first interface is connected to the second interface, the third interface is connected to the fourth interface, and the fifth interface is connected to the sixth interface;

[0127] "Inject" position (refer to Figure 3 ): The first interface is connected to the sixth interface, the third interface is connected to the second interface, and the fifth interface is connected to the fourth interface.

[0128] In addition, the high vacuum glass pistons (6, 8, 10) can only be in two positions (first position and second position), which are specifically defined as follows:

[0129] High vacuum glass piston (6):

[0130] First position: the sample gas is connected, and the piston rotates to connect the "sample injection pipeline (21) → high vacuum glass piston (6) → the fifth interface of the six-way valve (7)", and cuts off the connection with the spring-type air resistor (5);

[0131] Second position: the carrier gas is connected, and the piston rotates to connect the "spring-type gas resistor (5) → high vacuum glass piston (6) → the fifth interface of the six-way valve (7)", cutting off the connection with the sample injection pipeline (21).

[0132] High vacuum glass piston (8):

[0133] First position: controls the incoming gas to enter the concentrating column, and the piston rotates to connect the sixth interface of the six-way valve (7) → the high vacuum glass piston (8) → the inlet end of the concentrating column (11) and cuts off the connection with the inlet end of the fixed volume sampling valve (9), so as to allow the incoming gas to enter the concentrating column for enrichment;

[0134] The second position: one end of the fixed volume sampling valve is connected, and the piston is rotated to connect "the sixth interface of the six-way valve (7) → the high vacuum glass piston (8) → the inlet end of the fixed volume sampling valve (9)", and the connection with the inlet end of the concentration column (11) is cut off, so that the inlet end of the sampling valve (9) is only connected to the sixth interface of the six-way valve (7) through the high vacuum glass piston (8), which is used to detect the flow path carrier gas pushing the sample during sampling.

[0135] High vacuum glass piston (10):

[0136] First position: the circuit of the concentrating column is connected, the piston is rotated to connect "the outlet of the concentrating column (11) → the high vacuum glass piston (10) → the third interface of the six-way valve (7)", and the connection with the outlet of the sampling valve (9) is cut off, so that the outlet of the concentrating column (11) is only connected to the third interface of the six-way valve (7) through the high vacuum glass piston (10), and the sample gas or carrier gas can be emptied through the outlet of the concentrating column (11) → the six-way valve (7) → the bubbler (12), which is used to exhaust the main gas during enrichment.

[0137] The second position: the other end of the fixed volume sampling valve is connected, and the piston is rotated to connect "the outlet end of the fixed volume sampling valve (9) → the high vacuum glass piston (10) → the third interface of the six-way valve (7)", and the connection with the outlet end of the concentration column (11) is cut off, so that the outlet end of the sampling valve (9) is connected only to the third interface of the six-way valve (7) through the high vacuum glass piston (10), which is used to introduce the sample into the chromatographic detection system during injection.

[0138] 1. Test preparation: initial state (standby)

[0139] 1.1 Six-way valve (7) status: The default is in the "sampling (Load)" position. At this time, the first interface is connected to the second interface, the third interface is connected to the fourth interface, and the fifth interface is connected to the sixth interface;

[0140] 1.2 Piston status:

[0141] The high vacuum glass piston (6) is in the second position, connected to the carrier gas, and connected to the "spring-type air resistance (5) → the fifth interface of the six-way valve (7)", cutting off the connection with the spring-type air resistance (5);

[0142] The high vacuum glass piston (8) is in the first position, controlling the incoming gas to enter the concentration column, connecting the sixth interface of the six-way valve (7) to the inlet of the concentration column (11), and cutting off the connection with the inlet of the fixed volume sampling valve (9);

[0143] The high vacuum glass piston (10) is in the first position, connected to the circuit of the concentration column, and connected to the "concentration column (11) outlet → the third interface of the six-way valve (7)", and cuts off the connection with the outlet of the sampling valve (9).

[0144] 1.3 Constant volume sampling valve (9): closed.

[0145] 1.4 Flow direction:

[0146] 1.4.1 Concentration flow path: carrier gas passes through the spring-type air resistor (5) → the second position of the high vacuum glass piston (6) → the fifth interface of the six-way valve (7) → the sixth interface of the six-way valve (7) → the first position of the high vacuum glass piston (8) → the inlet end of the concentration column (11) → the outlet end of the concentration column (11) → the first position of the high vacuum glass piston (10) → the third interface of the six-way valve (7) → the fourth interface of the six-way valve (7) → the bubbler (12) → the wet flow meter (13) → emptying.

[0147] 1.4.2 Detection flow path: carrier gas passes through the pressure regulating valve (14) → pressure gauge (15) → first interface of the six-way valve (7) → second interface of the six-way valve (7) → vaporization chamber (18) → chromatographic column (19) → thermal conductivity cell (20).

[0148] At this time, the detection flow path carrier gas, which is precisely controlled by the pressure-stabilizing valve (14) and the needle valve (16), continuously flows in the chromatographic detection system at a constant flow rate of 30 mL / min and a stable pressure of 0.35 MPa, so that the baseline noise of the thermal conductivity cell detector (20) is ≤30 μV, providing a stable signal reference for high-sensitivity detection of trace impurities.

[0149] 2. Sample Injection and Enrichment

[0150] The control system starts the detection program, the multi-channel sampling switching system selects the target point, the corresponding solenoid valve opens, and the sample gas enters the sample sampling pipeline (21).

[0151] 2.1 Six-way valve (7) status: keep the "sampling (Load)" position, at this time, the first interface is connected to the second interface, the third interface is connected to the fourth interface, and the fifth interface is connected to the sixth interface.

[0152] 2.2 Piston status adjustment:

[0153] High vacuum glass piston (6): switch to the first position, connect the sample gas, connect the "sample injection pipeline (21) → the fifth interface of the six-way valve (7)", and cut off the connection with the spring-type air resistor (5);

[0154] High vacuum glass piston (8): maintains the first position, controls the incoming gas to enter the concentration column, connects the sixth interface of the six-way valve (7) to the inlet end of the concentration column (11), and cuts off the connection with the inlet end of the fixed volume sampling valve (9);

[0155] The high vacuum glass piston (10) is kept in the first position, connected to the circuit of the concentration column, connected to the outlet of the concentration column (11) → the third interface of the six-way valve (7), and cut off the connection with the outlet of the sampling valve (9).

[0156] 2.3 Constant volume sampling valve (9): closed.

[0157] 2.4 Flow direction:

[0158] 2.4.1 Sample injection path:

[0159] The sample gas (high-purity hydrogen, containing 0.5 ppm oxygen and nitrogen) passes through the sample injection line (21) → the first position of the high vacuum glass piston (6) → the fifth interface of the six-way valve (7) → the sixth interface of the six-way valve (7) → the first position of the high vacuum glass piston (8) → the inlet end of the concentration column (11);

[0160] 2.4.2 Enrichment and emptying pathways:

[0161] The sample gas enters the concentrator column (11) at a flow rate of 800-1000 mL / min, oxygen and nitrogen impurities are adsorbed by the 5A molecular sieve, and the main hydrogen gas passes through the outlet end of the concentrator column (11) → the first position of the high vacuum glass piston (10) → the third interface of the six-way valve (7) → the fourth interface of the six-way valve (7) → the bubbler (12) → the wet flow meter (13) → emptying;

[0162] The wet flow meter (13) measures a cumulative amount of 400 mL of sample gas, the enrichment time is 10 minutes, and the low-temperature environment of the concentration column is provided by an external liquid neon device.

[0163] 3. Sampling and Concentration Column Purging

[0164] After enrichment is completed, the control system sends a sampling instruction.

[0165] 3.1 Six-way valve (7) status: keep in “Sampling (Load)” position.

[0166] 3.2 Piston status adjustment:

[0167] The high vacuum glass piston (6) is switched to the second position, the carrier gas is connected, the "spring-type gas resistor (5) → the fifth interface of the six-way valve (7)" is connected, and the connection with the sample injection line (21) is cut off;

[0168] The high vacuum glass piston (8) is switched to the second position, connected to one end of the constant volume sampling valve, connected to the sixth interface of the six-way valve (7) → the inlet end of the constant volume sampling valve (9), and cut off the connection with the inlet end of the concentration column (11);

[0169] The high vacuum glass piston (10) is switched to the second position, connected to the other end of the constant volume sampling valve, and connected to the outlet of the constant volume sampling valve (9) → the third interface of the six-way valve (7), and cut off the connection with the outlet of the concentration column (11);

[0170] 3.3 Constant volume sampling valve (9): open state (volume 250 μL).

[0171] 3.4 Flow direction:

[0172] 3.4.1 Purge path:

[0173] The carrier gas (high-purity helium, 800 mL / min) in the concentrated flow path passes through the spring-type gas resistor (5) → the second position of the piston (6) → the fifth interface of the six-way valve (7) → the sixth interface of the six-way valve (7) → the second position of the piston (8) → the inlet end of the constant volume sampling valve (9) → the outlet end of the constant volume sampling valve (9) → the second position of the piston (10) → the third interface of the six-way valve (7) → the fourth interface of the six-way valve (7) → the bubbler (12) → emptying.

[0174] 3.4.2 Sampling and filling:

[0175] The enriched sample (containing 200 times concentrated oxygen and nitrogen, concentration 100 ppm) after analysis by the concentration column enters the fixed volume sampling valve (9) through the second position of the piston (8, 10), and the internal pressure is consistent with the auxiliary carrier gas (0.1 MPa), completing accurate quantification.

[0176] Among them, 3.4.1 purging and 3.4.2 sampling and filling can be carried out simultaneously.

[0177] 4. Injection Switching and Detection

[0178] After purging and sampling are completed, the control system sends the injection command.

[0179] 4.1 Six-way valve (7) status: quickly switch to the "Inject" position (switching time ≤ 0.5 seconds), at this time: the first interface is connected to the sixth interface, the third interface is connected to the second interface, and the fifth interface is connected to the fourth interface.

[0180] 4.2 Piston status:

[0181] High vacuum glass piston (6): maintain the second position, connect the carrier gas, and continuously purge the concentration column;

[0182] High vacuum glass piston (8): maintains the second position, and conducts "the sixth interface of the six-way valve (7) → the inlet end of the fixed volume sampling valve (9)";

[0183] High vacuum glass piston (10): maintains the second position, and conducts "the outlet of the fixed volume sampling valve (9) → the third interface of the six-way valve (7)".

[0184] 4.3 Constant volume sampling valve (9): open.

[0185] 4.4 Flow direction:

[0186] 4.4.1 Detection flow path:

[0187] Detection flow path carrier gas (through the pressure regulating valve 14, 30 mL / min, 0.35 MPa) → six-way valve (7) first interface → six-way valve (7) sixth interface → piston (8) second position → constant volume sampling valve (9) → piston (10) second position → six-way valve (7) third interface → six-way valve (7) second interface → vaporization chamber (18) → chromatographic column (19) → thermal conductivity cell (20);

[0188] Among them, 250 μL of enriched sample is desorbed in the vaporization chamber (180° C.), enters the chromatographic column (19) along with the detection flow carrier gas, and after the oxygen and nitrogen impurities are separated, enters the thermal conductivity cell (20) to generate an electrical signal.

[0189] 5. Purge reset and dual flow parallel preparation

[0190] After the detection is completed, the control system sends a reset command.

[0191] 5.1 Six-way valve (7) status: switch back to the "sampling (Load)" position. At this time, the first interface is connected to the second interface, the third interface is connected to the fourth interface, and the fifth interface is connected to the sixth interface.

[0192] 5.2 Piston status adjustment:

[0193] High vacuum glass piston (6): maintain the second position, connect the carrier gas, and continuously purge the concentration column and sampling valve;

[0194] The high vacuum glass piston (8) is switched to the first position to control the incoming gas to enter the concentration column, connect the sixth interface of the six-way valve (7) to the inlet of the concentration column (11), and cut off the connection with the inlet of the fixed volume sampling valve (9);

[0195] The high vacuum glass piston (10) is switched to the first position, connecting the circuit of the concentration column, connecting the outlet of the concentration column (11) to the third interface of the six-way valve (7), and cutting off the connection with the outlet of the sampling valve (9).

[0196] 5.3 Constant volume sampling valve (9): closed.

[0197] 5.4 Flow direction:

[0198] 5.4.1 Purge reset path:

[0199] The carrier gas in the concentrated flow path passes through the spring-type gas resistor (5) → the second position of the piston (6) → the fifth interface of the six-way valve (7) → the sixth interface of the six-way valve (7) → the first position of the piston (8) → the inlet end of the concentrated column (11) → the outlet end of the concentrated column (11) → the first position of the piston (10) → the third interface of the six-way valve (7) → the fourth interface of the six-way valve (7) → the bubbler (12) → emptying.

[0200] 5.4.2 Preparation of dual flow paths in parallel:

[0201] If dual-flow parallel analysis is enabled, the control system switches to the next point through the multi-channel injection switching system, and the piston (6) can be switched to the first position again to simultaneously enrich the next sample, thereby realizing the parallel operation of "while detecting the current sample, the low-temperature concentration system synchronously processes the next sample".

[0202] Based on Example 1, the positions of the six-way valve (7), high vacuum glass piston (6, 8, 10), and fixed volume sampling valve (9) at each stage are summarized in Table 1.

[0203] Table 1:

[0204]

[0205] Example 2: Detection of oxygen and nitrogen impurities in hydrogen (500-5000 ppm) in normal mode

[0206] 1. Activate the bypass analysis system: Use a quantitative tube (not shown in the figure) to inject the sample through the bypass six-way valve (not shown in the figure) provided on the bypass connecting tube (17), without concentration, and directly enter the chromatographic detection system for analysis and detection.

[0207] 2. Analysis process:

[0208] Carrier gas: through the pressure regulating valve (14) → bypass pressure gauge (15-1) → bypass vaporization chamber (18-1) → bypass chromatographic column (19-1) → thermal conductivity cell (20)

[0209] Sample gas: through quantitative tube (2mL) → bypass six-way valve (not shown) → bypass connecting tube (17) → bypass vaporization chamber (18-1) → bypass chromatographic column (19-1) → thermal conductivity cell (20).

[0210] Example 3: Online monitoring of the entire hydrogen liquefaction system

[0211] 1. First refer to Figure 4 , conduct a detailed analysis of the control process of the multi-channel injection automatic switching system:

[0212] S0: Receive instructions. After receiving the "debug mode" instruction from the host computer (Y1), enter S1; after receiving the "automatic mode" instruction from the host computer (Y2), enter S2;

[0213] S1: Enter "debugging mode". The relevant content of "automatic mode" is not displayed. The solenoid valve used for analysis is turned on / off on the interface, and the device is debugged manually to perform maintenance or troubleshooting.

[0214] S2: Click "Auto Mode" and a window will pop up. First, select the analysis path (analysis point), then choose whether to start "Continuous Analysis"; finally, set the purge time and number of analyses.

[0215] After S2 is set up and receives the "start" command (Y3) from the host computer, it enters S3;

[0216] S3: Controls the opening or closing of all solenoid valves;

[0217] Selecting to close all solenoid valves can return the system to its initial state;

[0218] Select a solenoid valve to open, such as selecting to open solenoid valve 1, and after judging that solenoid valve 1 is in the open state, enter S4;

[0219] S4: Taking solenoid valve 1 as an example, the logic is as follows:

[0220] Open solenoid valve 1 and purge according to the set purge time. After the purge is completed, determine whether the host computer has received the "stop" command.

[0221] Yes (Y4), go directly to S9;

[0222] No, send the chromatographic start pulse signal. After sending the chromatographic start pulse signal, determine again whether the host computer "stop" command is received.

[0223] Yes, jump to S9 after this analysis is completed;

[0224] No, the chromatograph is triggered to analyze, and the timing starts at 240s, the analysis time and analysis concentration are displayed, and the "number of analysis" is increased by 1. Then, it is determined whether the number of analysis is equal to the set value.

[0225] If no, return to the step of sending the chromatographic start pulse signal and continue the analysis (loop);

[0226] If yes, close solenoid valve 1, and then determine whether other solenoid valves 2, 3, 4, and 5 have been selected.

[0227] If yes, proceed to the corresponding steps (S5, S6, S7, S8);

[0228] No, determine whether to select continuous analysis.

[0229] If yes, return to S3 to re-determine whether to select solenoid valve 1 and enter continuous analysis;

[0230] No, go to S9.

[0231] S5-S8: correspond to solenoid valve 2-solenoid valve 5 respectively. The logic is consistent with S4. The purging, analysis, number judgment and closing operations of each injection are performed in sequence.

[0232] S9: Open solenoid valve 1, close solenoid valves 2-5, and determine whether the "stop purge" command from the host computer is received.

[0233] Yes, enter S10,

[0234] If not, keep solenoid valve 1 open and close solenoid valves 2-5 to reset the system, and continue to purge the gas line to keep it clean.

[0235] S10: Close solenoid valve 1.

[0236] 2. According to Figure 1 and Figure 2 , using a dual-flow gas chromatography device with a multi-channel injection switching system, full-process online monitoring of a total of 5 key monitoring points in the hydrogen liquefaction system is achieved.

[0237] 3. Parameter settings:

[0238] The purge time is set to 180s;

[0239] The number of analyses was set to 3;

[0240] Select "Continuous Mode", that is, after the 5-way loop analysis is completed, it returns to the first way to continue analysis.

[0241] 4. Operation process:

[0242] 4.1 Startup preparation and analysis of each point:

[0243] Click the "Automatic Mode" command on the host computer to initialize the system and close the solenoid valves of the non-selected routes.

[0244] Analysis of point 1:

[0245] Open the No. 1 solenoid valve and purge the compressor inlet air line for 180 seconds to remove residual impurities in the pipeline;

[0246] After the purge is completed, a 24V hydrogen gas chromatography start pulse signal is sent (connected for 1 second and then disconnected) to trigger the chromatograph to start analysis (timer 240 seconds);

[0247] The total time (purge + chromatographic analysis) is 360 s to complete the analysis of this circuit. Repeat the above purge-analysis process until three analyses are completed.

[0248] Cyclic analysis of points 2-5:

[0249] After the analysis of point 1 is completed three times, the solenoid valve No. 2 is automatically switched to open, and the gas path of point 2 is purged for 180 seconds. Then the chromatography start signal is sent to trigger the chromatograph to start analysis (timer 240 seconds), a total of 360 seconds of analysis, and the same is repeated three times;

[0250] Follow this process to complete three analyses of points 3, 4, and 5.

[0251] 4.2 Continuous mode cycle:

[0252] After the last analysis of point 5 is completed, the system automatically returns to the first path (point 1) and repeats the "purge-analysis" process to achieve continuous cycle monitoring.

[0253] 4.3 Analysis completed shutdown:

[0254] If you need to stop monitoring, click the "Stop Purge" command on the host computer. After the system completes the analysis of the current number of channels, it closes all solenoid valves, switches to valve No. 1 to open the purge (residual gas is emptied), and no longer sends the chromatographic start pulse. The system enters the standby state.

[0255] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present invention can make slight changes or modifications to equivalent embodiments using the above-mentioned technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A dual-flow gas chromatography device, characterized in that: include: Carrier gas purification system, used for purifying the carrier gas; a cryogenic concentration system connected to an output end of the carrier gas purification system; a chromatographic detection system connected to the output end of the carrier gas purification system and arranged in parallel with the cryogenic concentration system; a switching device for transferring the sample enriched by the cryogenic concentration system to the chromatographic detection system; Sample introduction system for delivering external samples to the cryoconcentration system.

2. The dual-flow path gas chromatography device according to claim 1, characterized in that: The switching time of the switching device is ≤ 0.5 seconds; Preferably, the switching device is a six-way valve, and the flow path switching between the low-temperature concentration system and the chromatographic detection system is achieved by switching the position of the six-way valve.

3. The dual-flow path gas chromatography device according to claim 1, characterized in that: The carrier gas purification system includes a carrier gas source and a purification unit connected in sequence through a pipeline, and the outlet end of the purification unit serves as the output end of the carrier gas purification system; Preferably, the purification unit comprises at least two stages of purification units; Preferably, the purification unit comprises a first-stage purification unit and a second-stage purification unit connected in sequence through a pipeline; Preferably, the first stage purification unit is a silica gel-5A molecular sieve room temperature adsorption tube, and the second stage purification unit is a 5A molecular sieve low temperature adsorption tube; Preferably, a pressure reducing gauge is provided between the carrier gas source and the purification unit.

4. The dual-flow path gas chromatography device according to claim 1, characterized in that: The low-temperature concentration system includes a concentration column and a fixed volume sampling device that are connected to each other; The inlet end of the concentrating column is connected to the output end of the carrier gas purification system; The fixed volume sampling device is connected to the switching device; Preferably, the fixed volume sampling device is a fixed volume sampling valve, which introduces the enriched sample into the chromatographic detection system through a switching device; Preferably, the low-temperature concentration system further comprises a bubbler and a wet flow meter connected in sequence through pipelines, and the inlet end of the bubbler is connected to the output end of the carrier gas purification system and / or the outlet end of the concentration column.

5. The dual-flow path gas chromatography device according to claim 1, characterized in that: The chromatographic detection system comprises a vaporization chamber, a chromatographic column, and a thermal conductivity cell which are sequentially connected through pipelines. The inlet end of the vaporization chamber is connected to a switching device and an output end of a carrier gas purification system.

6. The dual-flow path gas chromatography device according to claim 5, characterized in that: The dual-flow gas chromatography device also includes a bypass analysis system, which includes: The bypass pipe has an air inlet connected to the output of the carrier gas purification system and an air outlet connected to the thermal conductivity cell of the chromatographic detection system. The bypass pipe is provided with the following components in sequence along the direction of carrier gas flow: Bypass pressure gauge, used to monitor carrier gas pressure; A connecting tube, wherein a bypass injection device is installed on the connecting tube; a bypass vaporization chamber connected to the downstream end of the connecting pipe through a bypass pipe; A bypass chromatographic column, one end of which is connected to the bypass vaporization chamber, and the other end of which is connected to a thermal conductivity cell detector (20); Preferably, the bypass sampling device comprises a bypass six-way valve and a quantitative tube connected to each other, wherein the six-way valve is used to control the sample to enter the bypass pipeline through the quantitative tube, pass through the bypass vaporization chamber and the bypass chromatographic column, and then be detected by the thermal conductivity cell detector (20).

7. The dual-flow path gas chromatography device according to any one of claims 1 to 6, characterized in that: It also includes a multi-channel injection switching system, which is connected to the sample injection system, and the multi-channel injection switching system includes: Multiple injection branches, one end of each injection branch is used to connect to a different external sample source; the other end is connected to the sample injection system; Multiple solenoid valves, each of which is installed on a corresponding sampling branch pipe to control the on / off of the sampling branch pipe; A control system is electrically connected to the multiple solenoid valves and is used to automatically switch the solenoid valves on and off according to a preset timing to achieve online continuous sampling of different external sample sources.

8. A method for analyzing gas impurities using the dual-flow path gas chromatography apparatus according to any one of claims 1 to 7, comprising the following steps: Carrier gas purification and diversion: After being purified by the carrier gas purification system, the carrier gas is diverted to provide carrier gas for the cryogenic concentration system and the chromatographic detection system respectively; Sample concentration: The external sample enters the cryogenic concentration system through the sample injection system, and the target impurities are enriched at low temperature, and the main gas is exhausted; Sample injection switching: operating the switching device to allow the sample enriched with impurities to enter the chromatographic detection system through the switching device; Separation and detection: The sample is vaporized, separated and detected in the chromatographic detection system to obtain the target impurity analysis results.

9. The analysis method according to claim 8, characterized in that While the chromatographic detection system is separating and detecting the current sample, the low-temperature concentration system is connected to the next sample through the sample injection system and simultaneously performs concentration and enrichment, thereby realizing dual-flow parallel analysis; Preferably, the sample is high-purity hydrogen, and the target impurities are oxygen and / or nitrogen; Preferably, the carrier gas is high-purity hydrogen, which is diverted after oxygen and nitrogen impurities are removed by the purification unit; Preferably, in the sample concentration step, the main body of hydrogen is evacuated through a bubbler and a wet flow meter, and oxygen and nitrogen impurities are enriched in the concentration column; Preferably, the low temperature environment of the concentration column in the low temperature concentration system is provided by a device for externally connecting an inert medium, and the boiling point of the inert medium is lower than the boiling point of liquid nitrogen; Preferably, the low temperature environment of the concentration column in the low temperature concentration system is provided by an external liquid neon device, and the temperature is controlled at -245.9°C to -197°C; Preferably, the carrier gas flow rate of the cryogenic concentration system is 300-800 mL / min and the pressure is 0.3-0.5 MPa; Preferably, the carrier gas flow rate of the chromatographic detection system is 30-100 mL / min and the pressure is 0.2-0.3 MPa; Preferably, when constant analysis is required, the bypass analysis system is turned on, and the sample is injected through the bypass injection device on the connecting pipe. After the pressure is monitored by the bypass pressure gauge of the bypass pipe, the carrier gas carries the sample and passes through the bypass vaporization chamber and the bypass chromatographic column for separation in sequence, and is detected by the thermal conductivity cell detector to realize the switching of the micro / constant analysis mode.

10. Application of the device according to any one of claims 1 to 7 or the analysis method according to any one of claims 8 to 9 in full-process online monitoring of a hydrogen liquefaction system; Preferably, the device is connected to multiple analysis points of the hydrogen liquefaction system through a multi-channel sampling switching system, and automatically switches the sampling according to a preset time sequence; The detection data of the method is uploaded to the main control system of the hydrogen liquefaction system in real time, and is used to adjust the temperature and pressure parameters of the liquefaction process, thereby realizing the linkage between the analysis results and the process control; Preferably, the device is connected to at least five analysis sites of the hydrogen liquefaction system via a multi-channel sample switching system; Preferably, the preset timing is a single-channel purge time of 5-30 minutes and an analysis number of 1-5 times.

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