System and method for simultaneously and continuously measuring trace sulfur-containing compounds and carbon-containing compounds in hydrogen on line

Abstract

The invention relates to a system and a method for simultaneously and continuously measuring trace sulfur-containing compounds and carbon-containing compounds in hydrogen on line. The system comprises a sample inlet, a carbon-containing compound detection unit and a sulfur-containing compound detection unit, wherein the carbon-containing compound detection unit and the sulfur-containing compound detection unit are connected with the sample inlet in parallel; the carbon-containing compound detection unit comprises a first controller, a first sample injector, a quantitative loop, a first chromatographic column and a first enhanced plasma discharge detector which are communicated in sequence; the sulfur-containing compound detection unit comprises a second controller, a second sample injector, a trapping trap, a second chromatographic column and a second enhanced plasma discharge detector which are communicated in sequence. According to the system disclosed by the invention, qualitative and quantitative analysis of trace sulfur-containing compound and carbon-containing compound impurities in to-be-detected sample gas can be completed at the same time only through one-time sample introduction; and by using the system disclosed by the invention, the detection lower limit of the sulfur-containing compound and the carbon-containing compound is lower, and the detection error is small.

Description

Technical Field

[0001] This disclosure relates to a gas chromatograph, and more specifically, to a system and method for the simultaneous online continuous determination of trace sulfur-containing and carbon-containing compounds in hydrogen. Background Technology

[0002] Hydrogen energy, as a highly efficient, clean, low-carbon, environmentally friendly, and sustainable secondary energy source, is considered one of the most promising clean energy sources and an important component of the national new energy system. Hydrogen fuel cell vehicles are a crucial application platform for hydrogen energy. Currently, hydrogen is primarily produced from traditional fossil fuels, with a smaller portion derived from high-cost water electrolysis. Fossil fuels inevitably contain various carbon and sulfur impurities during hydrogen production. Research reports that even at 10×10⁻⁶... -9 Even trace amounts of sulfur-containing impurities at the mol / mol (10 ppb) level can cause irreversible performance degradation in fuel cells. Carbon monoxide can cause severe catalyst poisoning, significantly impacting the performance of the fuel cell powertrain. Carbon dioxide dilutes hydrogen and may affect the exhaust and recirculation blower control of the fuel cell powertrain. Very high concentrations of carbon dioxide can also be catalytically converted to carbon monoxide through a reverse water-gas shift reaction, thus poisoning the catalyst. Hydrocarbons (such as methane) can adsorb onto the catalyst layer, reducing the catalyst surface area and thus lowering battery performance. They may also decompose into carbon monoxide and adsorb onto the catalyst layer. To ensure the long-term stable operation of hydrogen fuel cells, the International Organization for Standardization (ISO), the Society of Automotive Engineers (SAE), and my country have all established corresponding standards for hydrogen used in PEMFCs, strictly limiting the purity of hydrogen and the content of various impurities. The ISO 14687:2019 and GB / T 37244-2018 standards stipulate that the total sulfur molar fraction shall not exceed 0.004 μmol / mol, the carbon monoxide molar fraction shall not exceed 0.2 μmol / mol, and the carbon dioxide molar fraction shall not exceed 2 μmol / mol. GB / T 37244-2018 stipulates that the total hydrocarbon (calculated as methane) molar fraction shall not exceed 2 μmol / mol, and ISO 14687:2019 stipulates that methane shall not exceed 100 μmol / mol.

[0003] The GB / T 37244-2018 product standard recommends using GC-SCD (sulfur chemiluminescence detector) for the detection of sulfur compounds in hydrogen. However, this method is a laboratory method, complex to operate, has a long detection cycle, carries transportation risks, cannot guarantee sample stability, and is unsuitable for online analysis. In addition to sulfur impurities, hydrogen produced from fossil fuels also contains carbon impurities such as carbon monoxide, carbon dioxide, and methane. GB / T 37244-2018 recommends using GB / T 8984-2008 for the detection of carbon monoxide and carbon dioxide. This method for industrial hydrogen uses methane conversion combined with gas chromatography-flame ionization detection, but the detection limit for carbon monoxide cannot meet the product specification requirements (less than 0.2 μmol / mol). Therefore, establishing an advanced, reliable, practical, and easy-to-operate online analytical technique for the simultaneous detection of sulfur and carbon impurities in hydrogen is crucial. Summary of the Invention

[0004] The purpose of this disclosure is to provide a system and method for the simultaneous online continuous determination of trace sulfur-containing compounds and carbon-containing compounds in hydrogen gas. This system can simultaneously perform qualitative and quantitative analysis of trace sulfur-containing compounds and carbon-containing compound impurities in the sample gas with only one injection, realizing continuous detection of the sample gas. Furthermore, the system of this disclosure has a lower detection limit for sulfur-containing compounds and carbon-containing compounds, smaller detection error, shorter detection cycle, and simpler operation.

[0005] To achieve the above objectives, a first aspect of this disclosure provides a system for simultaneously determining trace sulfur-containing compounds and carbon-containing compounds in a gas. The system includes an injection port and a carbon-containing compound detection unit and a sulfur-containing compound detection unit connected in parallel with the injection port. The carbon-containing compound detection unit includes a first controller, a first injector, a quantitative loop, a first chromatographic column, and a first enhanced plasma discharge detector, connected in sequence. The sulfur-containing compound detection unit includes a second controller, a second injector, a trap, a second chromatographic column, and a second enhanced plasma discharge detector, connected in sequence. The first injector includes a first sample inlet, a first sample outlet, a first carrier gas inlet, and a first carrier gas outlet. The first sample outlet is connected to the inlet of the quantitative loop, or the gas at the first sample outlet is directly vented. The first carrier gas outlet is convertibly connected to or not connected to the inlet of the first chromatographic column through the quantitative loop. The second injector includes a second sample inlet, a second sample outlet, a second carrier gas inlet, and a second carrier gas outlet; the second sample outlet is connected to the inlet of the trap, or the gas at the second sample outlet is directly vented; the second carrier gas outlet is convertibly connected to or not connected to the inlet of the second chromatographic column through the trap. The first sample inlet and the second sample inlet are respectively connected to the sample inlet.

[0006] Optionally, the first controller is a first needle valve; the first injector is a first six-way switching valve; the first six-way switching valve includes a first interface, a second interface, a third interface, a fourth interface, a fifth interface, and a sixth interface; the first interface is formed as the first carrier gas inlet, the first carrier gas inlet is connected to a first carrier gas pipeline, the second interface is connected to the inlet of the first chromatographic column, the third interface is connected to the outlet of the quantitative loop, the fourth interface is formed as the first sample outlet, the first sample outlet is connected to a first sample vent pipeline, the fifth interface is formed as the first sample inlet, the first sample inlet is connected to a first injection pipeline, and the sixth interface is connected to the inlet of the quantitative loop; The first needle valve has a closed state and an open state; the first six-way switching valve has a closed state and an open state; The first needle valve is in the open state, the first six-way switching valve is in the closed state, the first interface is connected to the second interface so that the first carrier gas inlet is connected to the inlet of the first chromatographic column, the fifth interface and the sixth interface are connected so that the first sample inlet is connected to the inlet of the quantitative loop (14), and the third interface and the fourth interface are connected so that the outlet of the quantitative loop is connected to the first sample outlet. The first needle valve is in the closed state, the first six-way switching valve is in the open state, the first interface is connected to the sixth interface so that the first carrier gas inlet is connected to the inlet of the metering loop, the fifth interface is connected to the fourth interface so that the first sample inlet and the first sample outlet are connected, and the third interface is connected to the second interface so that the outlet of the metering loop is connected to the inlet of the first chromatographic column.

[0007] Optionally, the second controller is a second needle valve; the second injector is a second six-way switching valve; the second six-way switching valve includes a seventh port, an eighth port, a ninth port, a tenth port, an eleventh port, and a twelfth port; the seventh port is formed as the second carrier gas inlet, the second carrier gas inlet is connected to a second carrier gas pipeline, the eighth port is connected to the inlet of the second chromatographic column, the ninth port is connected to the inlet of the trap, the tenth port is formed as the second sample outlet, the second sample outlet is connected to a second sample venting pipeline, the eleventh port is formed as the second sample inlet, the second sample inlet is connected to a second injection pipeline, and the twelfth port is connected to the outlet of the trap; The second needle valve has a closed state and an open state; the second six-way switching valve has a closed state and an open state; The second needle valve is in the open state, the second six-way switching valve is in the closed state, the seventh interface is connected to the eighth interface so that the second carrier gas inlet is connected to the inlet of the second chromatographic column, the eleventh interface is connected to the ninth interface so that the second sample inlet is connected to the inlet of the trap, and the twelfth interface is connected to the tenth interface so that the outlet of the trap is connected to the outlet of the second sample. The second needle valve is in the closed state, the second six-way switching valve is in the open state, the seventh interface is connected to the twelfth interface so that the second carrier gas inlet is connected to the inlet of the trap, the eleventh interface is connected to the tenth interface so that the second sample inlet and the second sample outlet are connected, and the ninth interface is connected to the eighth interface so that the outlet of the trap is connected to the inlet of the second chromatographic column.

[0008] Optionally, the first chromatographic column is a stainless steel micro-packed chromatographic column, the stationary phase is a carbon molecular sieve, the mesh size of the carbon molecular sieve is 80~120 mesh, the column length is 1~6m, and the inner diameter is 0.5~1.0mm; The second chromatographic column is an elastic quartz capillary column with polydimethylsiloxane as the stationary phase. The column length is 40-70 m and the inner diameter is 0.32-0.53 mm.

[0009] Optionally, the first enhanced plasma discharge detector includes a filter with a wavelength of 228 nm; The second enhanced plasma discharge detector includes a filter with a characteristic wavelength of 780 nm.

[0010] A second aspect of this disclosure provides a method for using the system described in the first aspect of this disclosure, the method comprising: The sample gas to be tested is introduced into the carbon-containing compound detection unit and the sulfur-containing compound detection unit through the inlet, respectively. After the gas sample to be tested is quantified by the quantitative loop, it enters the first chromatographic column under the carry gas for the first separation, and then the carbon-containing compound obtained by separation enters the first enhanced plasma discharge detector for detection. After the gas sample to be tested is captured and desorbed by the trap, the desorbed gas is carried by the carrier gas into the second chromatographic column for the second separation. Then, the sulfur-containing compounds obtained by separation are detected by the second enhanced plasma discharge detector.

[0011] Optionally, after the sample gas is quantified by the quantitative loop, it enters the first chromatographic column under the carry gas for the first separation, including: The first controller is a first needle valve, and the first injector is a first six-way switching valve. When the first controller is in the open state and the first six-way switching valve is in the closed state, the first sample inlet is connected to the inlet of the quantitative loop, so that the gas to be tested enters the quantitative loop for quantification. The first controller is switched to the off state, and the first six-way switching valve is set to the open state, so that the first carrier gas inlet is connected to the inlet of the quantitative loop, so that the carrier gas carries the sample gas to be tested in the quantitative loop into the first chromatographic column for the first separation process.

[0012] Optionally, the conditions for the first separation process include: being carried out at a constant temperature of 120~200℃; a carrier gas flow rate of 10~20mL / min; the carrier gas including helium; a flow rate of the sample gas to be tested of 10~30 mL / min; and a switching time of 20~40s.

[0013] Optionally, after the sample gas to be tested is captured and desorbed by the trap, the desorbed gas is carried by the carrier gas into the second chromatographic column for a second separation, including: The second controller is a second needle valve, and the second injector is a second six-way switching valve. The trap is set to the trapping temperature, the second controller is turned on, and the second six-way switching valve is turned off, so that the second sample inlet is connected to the inlet of the trapping trap, so that the gas to be tested enters the trapping trap for trapping. Set the trap to the desorption temperature, switch the second controller to the off state, and set the second six-way switching valve to the open state, so that the second carrier gas inlet is connected to the inlet of the trap, so that the carrier gas carries the desorbed gas in the trap into the second chromatographic column for the second separation process.

[0014] Optionally, the conditions for the second separation process include: an initial temperature of 30-50°C, held at the initial temperature for 5-10 min; an endpoint temperature of 200-240°C, held at the endpoint temperature for 10-20 min; a heating rate of 5-15°C / min; a carrier gas flow rate of 10-20 mL / min; the carrier gas includes helium; the flow rate of the sample gas to be tested is 30-70 mL / min; and the switching time is 100-300 s. The trapping temperature is -30 to -10°C, and the desorption temperature is 200 to 230°C.

[0015] Optionally, the detection limit of the method for sulfur-containing compounds is 0.1 nmol / mol, and the detection limit of the method for carbon-containing compounds is 0.01 μmol / mol.

[0016] The system disclosed herein, through the above technical solution, includes a carbon-containing compound detection unit and a sulfur-containing compound detection unit. It can simultaneously perform qualitative and quantitative analysis of trace sulfur-containing compounds and carbon-containing compound impurities in the sample gas with a single injection, achieving continuous detection of the sample. The system pre-concentrates sulfur-containing compounds online, removing a large amount of hydrogen substrate before separation and detection, effectively improving the detection sensitivity for trace sulfur-containing compounds and exhibiting high detection resolution for hydrogen sulfide. For carbon-containing compounds, the system uses a single controller, chromatographic column, and detector for analysis, achieving higher detection sensitivity and enabling detection at the nmol / mol level. The system is simple to configure, easy to operate, and has a short detection cycle, requiring only one valve switch to complete the analysis. Furthermore, the system offers lower detection limits and smaller detection errors for both sulfur-containing and carbon-containing compounds, making it convenient and quick to operate, and more suitable for detecting trace impurities in hydrogen gas used in proton exchange membrane fuel cells.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a system for simultaneously determining trace sulfur-containing compounds and carbon-containing compounds in hydrogen gas.

[0019] Figure 2 This is a chromatogram of sulfur-containing compounds measured in Example 1 of this disclosure.

[0020] Figure 3 This is a chromatogram of a carbon-containing compound obtained in Example 1 of this disclosure.

[0021] Explanation of reference numerals in the attached figures 1: Inlet; 2: First sample vent line; 3: Second sample vent line; 4: Second carrier gas line; 6: First carrier gas line; 7: First controller; 8: Second controller; 9: First injector; 10: Second injector; 11: Back pressure valve; 12: Back pressure valve; 14: Quantitative loop; 15: Trapping trap; 16: First chromatographic column; 17: Second chromatographic column; 20: First enhanced plasma discharge detector; 21: Second enhanced plasma discharge detector; 31: First injection line; 32: Second injection line; 33: Carbon-containing compound detection unit; 34: Sulfur-containing compound detection unit; 111: First port of the first six-way switching valve; 112: Sixth port of the first six-way switching valve; 113: Fifth port of the first six-way switching valve; 114: Fourth port of the first six-way switching valve; 115: Third port of the first six-way switching valve; 116: Second port of the first six-way switching valve; 221: The tenth port of the second six-way switching valve; 222: The twelfth port of the second six-way switching valve; 223: The seventh port of the second six-way switching valve; 224: The eighth port of the second six-way switching valve; 225: The ninth port of the second six-way switching valve; 226: The eleventh port of the second six-way switching valve. Detailed Implementation

[0022] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0023] The first aspect of this disclosure provides a system for simultaneously determining trace sulfur-containing compounds and carbon-containing compounds in hydrogen gas, such as... Figure 1As shown, the system includes an injection port 1 and a carbon-containing compound detection unit 33 and a sulfur-containing compound detection unit 34 connected in parallel with the injection port 1. The carbon-containing compound detection unit 33 includes a first controller 7, a first injector 9, a quantitative loop 14, a first chromatographic column 16, and a first enhanced plasma discharge detector 20 connected in sequence. The sulfur-containing compound detection unit 34 includes a second controller 8, a second injector 10, a trap 15, a second chromatographic column 17, and a second enhanced plasma discharge detector 21 connected in sequence. The first injector 9 includes a first sample inlet, a first sample outlet, a first carrier gas inlet, and a first carrier gas outlet. The outlet is connected to the inlet of the quantitative loop 14, or the gas from the first sample outlet is directly vented. The first carrier gas outlet is convertibly connected to or not connected to the inlet of the first chromatographic column 16 through the quantitative loop 14. The second injector 10 includes a second sample inlet, a second sample outlet, a second carrier gas inlet, and a second carrier gas outlet. The second sample outlet is connected to the inlet of the trap 15, or the gas from the second sample outlet is directly vented. The second carrier gas outlet is convertibly connected to or not connected to the inlet of the second chromatographic column 17 through the trap 15. The first sample inlet and the second sample inlet are respectively connected to the injection port 1.

[0024] The system disclosed herein includes a carbon-containing compound detection unit and a sulfur-containing compound detection unit. It can simultaneously perform qualitative and quantitative analysis of trace sulfur-containing compounds and carbon-containing compound impurities in the sample gas with a single injection, enabling continuous detection of the sample. The system pre-captures sulfur-containing compounds online, removing a large amount of hydrogen substrate before separation and detection, effectively improving the detection sensitivity for trace sulfur-containing compounds and providing high resolution for hydrogen sulfide. For carbon-containing compounds, the system uses a single controller, chromatographic column, and detector for analysis, achieving higher detection sensitivity and enabling detection at the nmol / mol level. The system is simple to configure, easy to operate, and has a short detection cycle, requiring only one valve opening and closing for analysis. Furthermore, the system offers lower detection limits and smaller detection errors for both sulfur-containing and carbon-containing compounds, making it convenient and quick to operate, and more suitable for the online continuous detection of relevant trace impurities in hydrogen used in proton exchange membrane fuel cells.

[0025] According to one embodiment of this disclosure, such as Figure 1As shown, the first controller is a first needle valve; the first injector 9 is a first six-way switching valve; the first six-way switching valve includes a first interface 111, a second interface 116, a third interface 115, a fourth interface 114, a fifth interface 113, and a sixth interface 112; the first interface 111 forms the first carrier gas inlet, which is connected to a first carrier gas line 6; the second interface 116 is connected to the inlet of the first chromatographic column 16; the third interface 115 is connected to the outlet of the quantitative loop 14; the fourth interface 114 forms the first sample outlet, which is connected to a first sample vent line 2; the fifth interface 113 forms the first sample inlet, which is connected to a first injection line 31; and the sixth interface 112 is connected to the inlet of the quantitative loop 14.

[0026] The carbon-containing compound detection unit disclosed herein uses only a single controller, a single chromatographic column, and a single detector to achieve qualitative and quantitative analysis of carbon-containing compounds at the nmol / mol content level. The carbon-containing compound detection unit has a simple configuration and a convenient operation process, requiring only one valve switch to complete the analysis. It has high detection sensitivity and is suitable for the analysis of trace impurities in hydrogen used in proton exchange membrane fuel cells.

[0027] According to one embodiment of this disclosure, such as Figure 1 As shown, the first needle valve has a closed state and an open state; the first six-way switching valve has a closed state and an open state; in one embodiment, the first needle valve is in the open state, the first six-way switching valve is in the closed state, the first interface 111 is connected to the second interface 116 so that the first carrier gas inlet is connected to the inlet of the first chromatographic column 16, the fifth interface 113 and the sixth interface 112 are connected so that the first sample inlet is connected to the inlet of the quantitative loop 14, and the third interface 115 and the fourth interface 114 are connected so that the outlet of the quantitative loop 14 is connected to the first sample outlet; the above embodiment can realize quantitative injection into the quantitative loop for quantification.

[0028] In another embodiment, the first needle valve is in the closed state, the first six-way switching valve is in the open state, the first interface 111 is connected to the sixth interface 112 so that the first carrier gas inlet is connected to the inlet of the metering loop 14, the fifth interface 113 is connected to the fourth interface 114 so that the first sample inlet and the first sample outlet are connected, and the third interface 115 is connected to the second interface 116 so that the outlet of the metering loop 14 is connected to the inlet of the first chromatographic column 16. This embodiment facilitates the carrier gas carrying a quantitative sample from the metering loop into the chromatographic column for component separation, and further into the enhanced plasma discharge detector 20 for detection and analysis.

[0029] In one embodiment, the carbon compound detection unit 33 further includes a back pressure valve 11, which is connected in parallel between the first sample inlet line 31 and the first sample vent line 2, and is used to control the sample inlet flow rate of the first sample.

[0030] According to one embodiment of this disclosure, the first chromatographic column 16 is a stainless steel micro-packed chromatographic column, the stationary phase is a carbon molecular sieve, the mesh size of the carbon molecular sieve can be 80-120 mesh, preferably 100-120 mesh, the column length is 1-6 m, preferably 2-4 m, and the inner diameter is 0.5-1.0 mm, preferably 0.75-1.0 mm. The above embodiment is beneficial for the effective separation of carbon-containing compounds.

[0031] According to one embodiment of this disclosure, the first enhanced plasma discharge detector 20 includes a filter with a wavelength of 228 nm. Compared to thermal conductivity detectors, the enhanced plasma discharge detector has higher detection sensitivity for carbon-containing compounds and is suitable for detecting impurities at the nmol / mol level. The above embodiment exhibits better response to carbon-containing compounds, higher sensitivity for their detection, and smaller error.

[0032] According to one embodiment of this disclosure, the carbon-containing compound may include one or more of carbon monoxide, carbon dioxide, and hydrocarbon compounds, wherein the hydrocarbon compounds may include one or more of methane, ethane, propane, n-butane, etc.

[0033] According to one embodiment of this disclosure, such as Figure 1 As shown, the second controller is a second needle valve; the second injector 10 is a second six-way switching valve; the second six-way switching valve includes a seventh port 223, an eighth port 224, a ninth port 225, a tenth port 221, an eleventh port 226, and a twelfth port 222; the seventh port 223 forms the second carrier gas inlet, which is connected to the second carrier gas line 4; the eighth port 224 is connected to the inlet of the second chromatographic column 17; the ninth port 225 is connected to the inlet of the trap 15; the tenth port 221 forms the second sample outlet, which is connected to the second sample vent line 3; the eleventh port 226 forms the second sample inlet, which is connected to the second injection line 32; and the twelfth port 222 is connected to the outlet of the trap 15.

[0034] The sulfur-containing compound detection unit disclosed herein pre-concentrates sulfur-containing compounds, traps and desorbs the sample gas using a trap, and then performs subsequent separation and detection of the desorbed gas. This removes a large amount of interference from the hydrogen matrix, improves detection sensitivity, and provides high resolution for hydrogen sulfide. The sulfur-containing compound detection unit disclosed herein uses only a single controller, a single chromatographic column, and a detector for the separation and detection of sulfur-containing compounds, making the configuration simpler and the operation process more convenient. Analysis can be completed with just one valve opening and closing, resulting in higher detection sensitivity and smaller errors.

[0035] According to one embodiment of this disclosure, such as Figure 1 As shown, the second needle valve 8 has a closed state and an open state; the second six-way switching valve 10 has a closed state and an open state; in one embodiment, the second needle valve 8 is in the open state and the second six-way switching valve 10 is in the closed state, so that the trap 15 is set to the trapping temperature, the seventh interface 223 is connected to the eighth interface 224 so that the second carrier gas inlet is connected to the inlet of the second chromatographic column 17, the eleventh interface 226 and the ninth interface 225 are connected so that the second sample inlet is connected to the inlet of the trap 15, and the twelfth interface 222 and the tenth interface 221 are connected so that the outlet of the trap 10 is connected to the second sample outlet. The above embodiment is beneficial for the trap to trap sulfur-containing compound components in the sample, removing a large amount of interference from the hydrogen substrate and improving the detection sensitivity of sulfur-containing compounds.

[0036] In another implementation, such as Figure 1 As shown, the trap 15 is set to the desorption temperature to release the trapped mixed sulfur-containing compound components. The second needle valve 8 is closed, the second six-way switching valve 10 is open, the seventh port 223 is connected to the twelfth port 222 to connect the second carrier gas inlet to the inlet of the trap 15, the eleventh port 226 is connected to the tenth port 221 to connect the second sample inlet and the second sample outlet, and the ninth port 225 is connected to the eighth port 224 to connect the outlet of the trap 15 to the inlet of the second chromatographic column 17. This embodiment facilitates the carrier gas carrying the desorbed gas from the trap into the second chromatographic column 17 for component separation, and further into the enhanced plasma discharge detector 21 for detection.

[0037] In one embodiment, the sulfur-containing compound detection unit 34 further includes a back pressure valve 12, which is connected in parallel between the second sample inlet line 32 and the second sample vent line 3, and is used to control the sample inlet flow rate of the first sample.

[0038] According to one embodiment of this disclosure, the second chromatographic column 17 is an elastic quartz capillary column, the stationary phase is polydimethylsiloxane, the column length is 40-70 m, preferably 50-60 m, and the inner diameter is 0.32-0.53 mm, preferably 0.53 mm. This embodiment is advantageous for the effective separation of sulfur-containing compounds.

[0039] According to one embodiment of this disclosure, the filler used in the trap is not specifically limited and can be a conventional filler in the art, such as Tenax composite filler or a composite filler containing silica gel and graphitized carbon black.

[0040] According to one embodiment of this disclosure, the second enhanced plasma discharge detector 21 includes a filter with a characteristic wavelength of 780 nm. The above embodiment exhibits better response to sulfur-containing compounds, resulting in more sensitive detection of sulfur-containing compounds and smaller errors.

[0041] According to one embodiment of this disclosure, all connecting pipes and interfaces in the sulfur-containing compound detection unit 34 are inertized, for example, using silanized stainless steel pipes. This embodiment avoids the adsorption of sulfur-containing compounds by the system, further improving the accuracy and sensitivity of sulfur-containing compound detection.

[0042] According to one embodiment of this disclosure, the sulfur-containing compound may include different forms of sulfur-containing compounds, such as one or more of hydrogen sulfide, carbonyl sulfide, ethanethiol, methyl sulfide, carbon disulfide, thiophene, and dimethyl disulfide.

[0043] A second aspect of this disclosure provides a method for using the system described in the first aspect of this disclosure, the method comprising: The sample gas to be tested is introduced into the carbon-containing compound detection unit 33 and the sulfur-containing compound detection unit 34 through the inlet 1, respectively. After the gas sample to be tested is quantified by the quantitative loop 14, it enters the first chromatographic column 16 under the carry of the carrier gas for the first separation, and then the carbon-containing compound obtained by separation enters the first enhanced plasma discharge detector 20 for detection. The gas sample to be tested is captured and desorbed by the trap 15 to obtain the desorbed gas, which is then carried by the carrier gas into the second chromatographic column 17 for the second separation. The sulfur-containing compounds obtained by the separation are then detected by the second enhanced plasma discharge detector 21.

[0044] This disclosed method employs different injection methods for carbon-containing and sulfur-containing compounds. A quantitative loop injection is used for carbon-containing compounds, while a trapping trap is used for sulfur-containing compounds for capture and desorption. This allows the two detection units to simultaneously analyze the samples under matched injection flow rates and carrier gas velocities. The two units separate and detect different components under suitable and non-interfering separation conditions, enabling simultaneous detection of the sample gas and achieving online continuous analysis. This method reduces the switching and connection of controllers and chromatographic columns, simplifies operation, shortens the detection cycle, and provides more accurate results, making it more suitable for the online continuous detection of trace impurities in hydrogen used in proton exchange membrane fuel cells.

[0045] According to one embodiment of this disclosure, after the sample gas is quantified by the quantitative loop 14, it enters the first chromatographic column 16 under the carry of the carrier gas for first separation, including: The first controller 7 is a first needle valve, and the first injector 9 is a first six-way switching valve. When the first controller is in the open state and the first six-way switching valve is in the closed state, the first sample inlet is connected to the inlet of the quantitative loop 14 so that the sample gas to be tested enters the quantitative loop for quantification. Switch the first controller to the off state and the first six-way switching valve to the open state, so that the first carrier gas inlet is connected to the inlet of the quantitative loop 14, so that the carrier gas carries the sample gas to be tested in the quantitative loop into the first chromatographic column for the first separation process.

[0046] According to one embodiment of this disclosure, the conditions for the first separation process include: being carried out at a constant temperature of 120-200°C, preferably 150-180°C; a carrier gas flow rate of 10-20 mL / min, preferably 15-18 mL / min; the carrier gas comprising helium; a sample gas flow rate of 10-30 mL / min, preferably 15-20 mL / min; and a switching time of 20-40 s, preferably 25-30 s. In the above embodiment, separating carbon-containing compounds using a separate temperature control unit is beneficial for improving detection sensitivity, resulting in more accurate detection results and smaller errors.

[0047] According to one embodiment of this disclosure, the sample gas to be tested is captured and desorbed by the trap 15 to obtain the desorbed gas, which then enters the second chromatographic column 17 under the carry of the carrier gas for a second separation, including: The second controller 8 is a second needle valve, the second injector 10 is a second six-way switching valve, and the trap 15 is set to the trapping temperature. The second controller is set to the open state, and the second six-way switching valve is set to the closed state, so that the second sample inlet is connected to the inlet of the trap 15, so that the sample gas to be tested enters the trap for trapping. Set the trap 15 to the desorption temperature to release the trapped mixed sulfur-containing compound components and obtain the desorbed gas. Switch the second controller to the off state and set the second six-way switching valve to the open state to connect the second carrier gas inlet with the inlet of the trap 15 so that the carrier gas carries the desorbed gas mixture in the trap into the second chromatographic column for the second separation process.

[0048] According to one embodiment of this disclosure, the conditions for the second separation process include: an initial temperature of 30-50°C, preferably 35-40°C; a holding time at the initial temperature of 5-10 min, preferably 6-8 min; an endpoint temperature of 200-240°C, preferably 210-220°C, a holding time at the endpoint temperature of 10-20 min, preferably 15-18 min; a heating rate of 5-15°C / min, preferably 8-10°C / min; a carrier gas flow rate of 10-20 mL / min, preferably 12-15 mL / min; the carrier gas comprising helium; a flow rate of the sample gas to be tested of 30-70 mL / min, preferably 40-60 mL / min; and a switching time of 100-300 s, preferably 120-200 s.

[0049] According to one embodiment of this disclosure, the trapping temperature is -30 to -10°C, preferably -20 to -30°C, and the desorption temperature is 200 to 230°C, preferably 210 to 220°C. In this embodiment, the sulfur-containing compounds are separated using a separate temperature control unit, which improves detection sensitivity, results in more accurate values, and reduces errors.

[0050] According to one embodiment of this disclosure, the detection includes qualitative analysis and quantitative analysis, wherein the qualitative analysis is performed by comparing the retention times of each component in a standard substance.

[0051] According to one embodiment of this disclosure, the quantitative analysis is performed using an external standard method based on the response values ​​of components flowing from enhanced plasma discharge detectors 20 and 21, to quantitatively analyze sulfur-containing compound impurities and carbon-containing compound components. Specifically, the external standard method involves preparing standard samples containing known amounts of various target components from the sample to be tested. Under the same analytical conditions, the standard samples and the sample to be tested are analyzed separately. The content of a component in the sample to be tested is determined by the response values ​​of the same components in the sample to be tested and the standard samples.

[0052] According to one embodiment of this disclosure, the method has a detection limit of 0.1 nmol / mol for sulfur-containing compounds and a detection range of 0.5 nmol / mol to 1000 nmol / mol; the method has a detection limit of 0.01 μmol / mol for carbon-containing compounds and a detection range of 0.05 μmol / mol to 10 μmol / mol.

[0053] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0054] The first chromatographic column 16 used in this disclosure is a ShinCarbon ST micro-packed gas chromatographic column manufactured by Restek Corporation. The stationary phase is a carbon molecular sieve with a mesh size of 100-120 mesh. The column length is 4m and the inner diameter is 0.53mm.

[0055] The second chromatographic column 17 used in this disclosure is a DB-1 capillary column, with polydimethylsiloxane as the stationary phase, a column length of 60 m, and an inner diameter of 0.53 mm.

[0056] The packing material used in the trapping trap disclosed herein is Restek's Tenax composite packing material.

[0057] Example 1 This embodiment adopts Figure 1The system shown includes: the carbon compound detection unit 33 uses a Restek ShinCarbon ST micro-packed gas chromatograph column 16 with a mesh size of 100-120 mesh, a column length of 4m, and an inner diameter of 0.53mm; an enhanced plasma discharge detector 20 is equipped with a 228nm feature filter; the interfaces in the six-way switching valve 9 are all made of 1 / 16-inch stainless steel tubing, and the joints between the tubing diameters are all 1 / 16-inch; the sulfur compound detection unit 34 uses a DB-1 capillary column 17 with a column length of 60m and an inner diameter of 0.53mm; an enhanced plasma discharge detector 21 is equipped with a 780nm feature filter; the interfaces in the six-way switching valve 10 are all made of 1 / 16-inch silanized stainless steel tubing, and the joints between the tubing diameters are all 1 / 16-inch silanized joints.

[0058] use Figure 1 A systematic method for determining trace sulfur and carbon compounds in gases, the method comprising: The gas sample to be tested is introduced into the carbon compound detection unit 33 and the sulfur compound detection unit 34 through the injection port 1, respectively. The first controller 7 is the first needle valve, and the first injector 9 is the first six-way switching valve. When the first controller is in the open state and the first six-way switching valve is in the closed state, the first sample inlet is connected to the inlet of the quantitative loop 14 so that the gas of the sample to be tested can enter the quantitative loop for quantification. The first controller is switched to the off state, and the first six-way switching valve is set to the open state, so that the first carrier gas inlet is connected to the inlet of the metering loop 14, so that the carrier gas carries the sample gas to be tested in the metering loop into the first chromatographic column 16 for the first separation process; then the separated carbon-containing compounds are sent to the first enhanced plasma discharge detector 20 for detection. The second controller 8 is the second needle valve, and the second injector 10 is the second six-way switching valve. The temperature of the trap 15 is set to the trapping temperature, the second controller is in the open state, and the second six-way switching valve is in the closed state, so that the second sample inlet is connected to the inlet of the trapping trap, so that the gas to be tested can enter the trapping trap for trapping. The temperature of the trap 15 is set to the desorption temperature to release the trapped mixed sulfur-containing compound components. The second controller is switched to the off state, and the second six-way switching valve is set to the open state to connect the second carrier gas inlet with the inlet of the trap, so that the carrier gas carries the desorbed gas in the trap into the second chromatographic column 17 for the second separation process. Then, the separated sulfur-containing compounds are sent to the second enhanced plasma discharge detector 21 for detection. Specific operating conditions are shown in Table 1. The gas sample was analyzed. The sample gas in Example 1 was a hydrogen gas sample containing trace amounts of hydrogen sulfide, carbonyl sulfide, ethanethiol, methyl sulfide, carbon disulfide, thiophene, dimethyl disulfide, carbon monoxide, carbon dioxide, and methane. The composition is shown in Table 2. The analytical results are shown in Table 2, and the obtained analytical chromatogram is shown below. Figure 2 and Figure 3 As shown.

[0059] Table 1

[0060] In Table 1, the "closed" state of each six-way switching valve is as follows: Figure 1 The connection is shown as shown; the "open" state is indicated by a dashed line connection.

[0061] Table 2

[0062] As shown in Table 2, the system disclosed herein can simultaneously analyze trace sulfur and carbon compounds in the sample in a single online injection. Furthermore, the system is convenient, quick, easy to operate, has a short detection cycle, accurate results, and small errors, making it more suitable for the online detection of trace sulfur and carbon compounds in hydrogen used in proton exchange membrane fuel cells.

[0063] Comparative Example 1 The method used in this comparative example is the same as in Example 1, except that the trap 15 of the sulfur-containing compound detection unit is replaced with a quantitative loop, and the sulfur-containing compounds are not pre-concentrated online. The analytical results are shown in Table 2.

[0064] Example 2 The system and method in this embodiment are the same as in embodiment 1, except that the gas sample in this embodiment is a sample containing methane and ethane. The analysis conditions are shown in Table 3, and the analysis results are shown in Table 4.

[0065] Table 3

[0066] The "closed" state of each six-way valve in Table 3 is as follows: Figure 1 The solid lines indicate the "open" state, while the dashed lines indicate the "on" state.

[0067] Table 4

[0068] As shown in Table 4, the system disclosed herein can simultaneously perform quantitative and qualitative analysis of trace sulfur-containing compounds and carbon-containing compounds in the sample by single online injection. Carbon-containing compounds include hydrocarbons such as methane and ethane. Furthermore, the system disclosed herein is convenient, quick, easy to operate, has a short detection cycle, and provides more accurate detection results with small errors.

[0069] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0070] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0071] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A system for simultaneous online continuous determination of trace sulfur-containing compounds and carbon-containing compounds in hydrogen gas, characterized in that, The system includes an injection port (1) and a carbon-containing compound detection unit (33) and a sulfur-containing compound detection unit (34) connected in parallel with the injection port (1); the carbon-containing compound detection unit (33) includes a first controller (7), a first injector (9), a quantitative loop (14), a first chromatographic column (16), and a first enhanced plasma discharge detector (20) connected in sequence; the sulfur-containing compound detection unit (34) includes a second controller (8), a second injector (10), a trap (15), a second chromatographic column (17), and a second enhanced plasma discharge detector (21) connected in sequence. The first injector (9) includes a first sample inlet, a first sample outlet, a first carrier gas inlet and a first carrier gas outlet. The first sample outlet is connected to the inlet of the quantitative loop (14), or the gas at the first sample outlet is directly vented. The first carrier gas outlet is either connected to or not connected to the inlet of the first chromatographic column (16) through the quantitative loop (14). The second sample injector (10) includes a second sample inlet, a second sample outlet, a second carrier gas inlet, and a second carrier gas outlet; the second sample outlet is connected to the inlet of the trap (15), or the gas at the second sample outlet is directly vented; the second carrier gas outlet is convertibly connected to or not connected to the inlet of the second chromatographic column (17) through the trap (15). The first sample inlet and the second sample inlet are respectively connected to the sample inlet (1).

2. The system according to claim 1, wherein, The first controller is a first needle valve; the first injector (9) is a first six-way switching valve; the first six-way switching valve includes a first interface (111), a second interface (116), a third interface (115), a fourth interface (114), a fifth interface (113) and a sixth interface (112); the first interface (111) is formed as the first carrier gas inlet, the first carrier gas inlet is connected to a first carrier gas pipeline (6), the second interface (116) is connected to the inlet of the first chromatographic column (16), the third interface (115) is connected to the outlet of the quantitative loop (14), the fourth interface (114) is formed as the first sample outlet, the first sample outlet is connected to a first sample venting pipeline (2), the fifth interface (113) is formed as the first sample inlet, the first sample inlet is connected to a first injection pipeline (31), and the sixth interface (112) is connected to the inlet of the quantitative loop (14); The first needle valve has a closed state and an open state; the first six-way switching valve has a closed state and an open state; The first needle valve is in the open state, the first six-way switching valve is in the closed state, the first interface (111) is connected to the second interface (116) so that the first carrier gas inlet is connected to the inlet of the first chromatographic column (16), the fifth interface (113) and the sixth interface (112) are connected so that the first sample inlet is connected to the inlet of the quantitative loop (14), and the third interface (115) and the fourth interface (114) are connected so that the outlet of the quantitative loop (14) is connected to the first sample outlet. The first needle valve is in the closed state, the first six-way switching valve is in the open state, the first interface (111) is connected to the sixth interface (112) so that the first carrier gas inlet is connected to the inlet of the quantitative loop (14), the fifth interface (113) is connected to the fourth interface (114) so ​​that the first sample inlet and the first sample outlet are connected, and the third interface (115) is connected to the second interface (116) so that the outlet of the quantitative loop (14) is connected to the inlet of the first chromatographic column (16).

3. The system according to claim 1, wherein, The second controller is a second needle valve; the second injector (10) is a second six-way switching valve; the second six-way switching valve includes a seventh port (223), an eighth port (224), a ninth port (225), a tenth port (221), an eleventh port (226), and a twelfth port (222); the seventh port (223) is formed as the second carrier gas inlet, the second carrier gas inlet is connected to a second carrier gas line (4), the eighth port (224) is connected to the inlet of the second chromatographic column (17), the ninth port (225) is connected to the inlet of the trap (15), the tenth port (221) is formed as the second sample outlet, the second sample outlet is connected to a second sample vent line (3), the eleventh port (226) is formed as the second sample inlet, the second sample inlet is connected to a second injection line (32), and the twelfth port (222) is connected to the outlet of the trap (14); The second needle valve has a closed state and an open state; the second six-way switching valve has a closed state and an open state; The second needle valve is in the open state, the second six-way switching valve is in the closed state, the seventh interface (223) is connected to the eighth interface (224) so ​​that the second carrier gas inlet is connected to the inlet of the second chromatographic column (17), the eleventh interface (226) and the ninth interface (225) are connected so that the second sample inlet is connected to the inlet of the trap (15), and the twelfth interface (222) and the tenth interface (221) are connected so that the outlet of the trap (10) is connected to the second sample outlet; The second needle valve is in the closed state, the second six-way switching valve is in the open state, the seventh port (223) is connected to the twelfth port (222) so that the second carrier gas inlet is connected to the inlet of the trap (15), the eleventh port (226) is connected to the tenth port (221) so that the second sample inlet and the second sample outlet are connected, and the ninth port (225) is connected to the eighth port (224) so ​​that the outlet of the trap (10) is connected to the inlet of the second chromatographic column (17).

4. The system according to claim 1, wherein, The first chromatographic column (16) is a stainless steel micro-packed chromatographic column, the stationary phase is a carbon molecular sieve, the mesh size of the carbon molecular sieve is 80~120 mesh, the column length is 1~6m, and the inner diameter is 0.5~1.0mm; The second chromatographic column (17) is an elastic quartz capillary column with polydimethylsiloxane as the stationary phase. The column length is 40~70m and the inner diameter is 0.32~0.53mm.

5. The system according to claim 1, wherein, The first enhanced plasma discharge detector (20) includes a filter with a wavelength of 228 nm; The second enhanced plasma discharge detector (21) includes a filter with a characteristic wavelength of 780 nm.

6. A method employing the system described in any one of claims 1 to 5, characterized in that, The method includes: The sample gas to be tested is introduced into the carbon-containing compound detection unit (33) and the sulfur-containing compound detection unit (34) respectively through the inlet (1). After the gas sample to be tested is quantified by the quantitative loop (14), it enters the first chromatographic column (16) under the carry of the carrier gas for the first separation, and then the carbon-containing compound obtained by separation enters the first enhanced plasma discharge detector (20) for detection; After the gas to be tested is captured and desorbed by the trap (15), the desorbed gas is carried by the carrier gas into the second chromatographic column (17) for the second separation. Then the sulfur-containing compounds obtained by separation are detected by the second enhanced plasma discharge detector (21).

7. The method according to claim 6, wherein, After the sample gas is quantified by the quantitative loop (14), it enters the first chromatographic column (16) under the carry gas for the first separation, including: The first controller (7) is a first needle valve, and the first injector (9) is a first six-way switching valve. The first controller is set to the open state, and the first six-way switching valve is set to the closed state, so that the first sample inlet is connected to the inlet of the quantitative loop (14), so that the sample gas to be tested enters the quantitative loop for quantification. Switch the first controller to the off state and set the first six-way switching valve to the open state, so that the first carrier gas inlet is connected to the inlet of the quantitative loop (9), so that the carrier gas carries the sample gas to be tested in the quantitative loop into the first chromatographic column for the first separation process.

8. The method according to claim 7, wherein, The conditions for the first separation process include: being carried out at a constant temperature of 120~200℃; a carrier gas flow rate of 10~20mL / min; the carrier gas including helium; a flow rate of the sample gas to be tested of 10~30 mL / min; and a switching time of 20~40s.

9. The method according to claim 6, wherein, The sample gas to be tested is captured and desorbed by the trap (15), and the desorbed gas is then carried by the carrier gas into the second chromatographic column (17) for a second separation, including: The second controller (8) is a second needle valve, and the second injector (10) is a second six-way switching valve. The trap (15) is set to the trapping temperature, the second controller is set to the open state, and the second six-way switching valve is set to the closed state. The second sample inlet is connected to the inlet of the trap (15) so that the gas to be tested enters the trap for trapping. Set the trap (15) to the desorption temperature, switch the second controller to the off state, and set the second six-way switching valve to the open state, so that the second carrier gas inlet is connected to the inlet of the trap (15), so that the carrier gas carries the desorbed gas in the trap into the second chromatographic column for the second separation process.

10. The method according to claim 9, wherein, The conditions for the second separation process include: an initial temperature of 30-50°C, held at the initial temperature for 5-10 min; an endpoint temperature of 200-240°C, held at the endpoint temperature for 10-20 min; a heating rate of 5-15°C / min; a carrier gas flow rate of 10-20 mL / min; the carrier gas includes helium; the flow rate of the sample gas to be tested is 30-70 mL / min; and the switching time is 100-300 s. The trapping temperature is -30 to -10°C, and the desorption temperature is 200 to 230°C.

11. The method according to claim 6, wherein, The method has a detection limit of 0.1 nmol / mol for sulfur-containing compounds and a detection limit of 0.01 μmol / mol for carbon-containing compounds.

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