A system and method for detecting trace impurities in hydrogen gas

Abstract

The present disclosure relates to a detection system and method for trace impurities in hydrogen, which comprises a sample processing module, an exogenous gas supply module, a control gas preparation module, a detection module and a tail gas processing module. The sample processing module comprises a sample supply submodule, a first three-way valve and a system pretreatment submodule. The exogenous gas supply module comprises a hydrogen supply submodule and a nitrogen supply submodule. The detection module comprises an infrared spectrometer and a gas cell. The detection system is simple to operate. Using the detection system, multiple trace impurities in hydrogen can be detected simultaneously in one detection. The detection system has the advantages of low detection limit, high detection precision, good repeatability and safe and green emission of hydrogen-containing tail gas.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of instrumental analysis, in particular to a detection system and method for trace impurities in hydrogen. BACKGROUND

[0002] As a secondary energy, hydrogen energy has multiple advantages such as diverse sources, zero terminal emissions, and wide applications. Fuel cell vehicles (FCV) are one of the important carriers of hydrogen energy. FCV is a kind of electric vehicle driven by electric energy, which is generated by electrochemical catalytic conversion of hydrogen in the fuel cell (proton exchange membrane PEMFC is the core component).

[0003] Hydrogen is mainly derived from traditional processes such as natural gas reforming, catalytic reforming by-product hydrogen, and coal hydrogen production. During the preparation process, hydrogen will inevitably contain trace impurities such as CO, CO2, NH3, hydrocarbons, sulfides, formaldehyde, formic acid, and inert gases. These trace impurities are one of the main factors affecting the durability of fuel cells.

[0004] Specifically, in the hydrogen used for fuel cells, trace CO, formic acid, and formaldehyde will be adsorbed on the catalyst, causing serious catalyst poisoning; CO2 will dilute hydrogen, affecting the exhaust and circulating blower control of the fuel cell powertrain, and high concentration of CO2 will also be catalytically converted into CO through the reverse water-gas shift reaction, thereby causing catalyst poisoning; water may cause the vehicle-mounted fuel system to easily freeze at low temperatures, resulting in reduced fuel cell efficiency; ammonia may cause the mass transfer capacity of the fuel cell electrolyte membrane to decrease, causing irreversible degradation of fuel cell performance; some hydrocarbons will be adsorbed on the catalyst layer, reducing the catalyst surface area and thus reducing the battery performance, and may also be decomposed into carbon monoxide and then adsorbed on the catalyst layer. Therefore, quantitative analysis of trace key impurities in the hydrogen source for FCV is of great significance for the further development of fuel cells.

[0005] In order to ensure the quality of hydrogen for FCV, the state has formulated GB / T 37244 “Fuel Hydrogen for Proton Exchange Membrane Fuel Cell Vehicles” in 2018. The standard clearly states the types and contents of 13 kinds of impurities that affect the performance of the battery, including the requirements that the content of formic acid and CO is <0.2×10 -6 mol / mol, the content of CO2 is <2×10 -6 mol / mol, the total hydrocarbon content is <2×10 - 6 mol / mol, the content of H2O is <5×10 -6 mol / mol, and the content of NH3 is <2×10 -6mol / mol, HCHO content <0.01×10 -6 The total concentration of CO, HCOOH, and HCHO should not exceed 0.2 × 10⁻⁶ mol / mol (ISO 14687-19 specifies that this concentration should not exceed 0.2 × 10⁻⁶ mol / mol). -6 mol / mol).

[0006] In related technologies, formaldehyde detection uses GB / T 16129 "Standard Method for Hygienic Examination of Formaldehyde in Residential Atmosphere - Spectrophotometric Method". This method requires pre-absorption of the sample, involves a large sample volume, and requires multiple reagents such as sulfuric acid, making the determination process cumbersome. Formic acid detection often uses HJ 1004-2018 "Determination of Organic Acids (Acetic Acid, Formic Acid and Oxalic Acid) in Ambient Air Precipitation - Ion Chromatography" and GB / T17068-1997 "Gas Chromatographic Determination of Formic Acid in Workshop Air", etc. These methods cannot meet the detection limit requirements of hydrogen for FCV. Carbon monoxide and carbon dioxide detection often use GB / T8984-2008 "Determination of Carbon Monoxide, Carbon Dioxide and Hydrocarbons in Gases - Gas Chromatography", etc.

[0007] The methods described above can only detect some of the trace impurities in hydrogen used in FCVs. There is a lack of methods that can simultaneously detect all nine trace impurities in hydrogen used in FCVs. Moreover, all of the above methods require absorption followed by determination, which results in cumbersome operation and large detection errors. Summary of the Invention

[0008] The purpose of this disclosure is to address the problems of existing methods that can only detect some impurities in trace impurities in hydrogen, and that are cumbersome to operate and have large detection errors, by providing a system and method for detecting trace impurities in hydrogen.

[0009] To achieve the above objectives, this disclosure provides a detection system for trace impurities in hydrogen. The detection system includes a sample processing module, an external gas supply module, and a detection module. The sample processing module includes a sample supply submodule, a first three-way valve, and a system pretreatment submodule. The external gas supply module includes a hydrogen supply submodule and a nitrogen supply submodule. The detection module includes an infrared spectrometer and a gas cell.

[0010] The sample supply submodule and the system preprocessing submodule are respectively connected to any two openings of the first three-way valve, and the remaining opening of the first three-way valve is connected to the inlet of the gas pool; the sample supply submodule is used to supply the hydrogen to be tested into the gas pool, and the system preprocessing submodule is used to perform equilibration preprocessing on the detection module.

[0011] The outlet of the hydrogen supply submodule is connected to the inlet of the gas pool, and the outlet of the nitrogen supply submodule is connected to the gas inlet of the infrared spectrometer. The hydrogen supply submodule is used to supply hydrogen to the gas pool to purge the gas pool, and the nitrogen supply submodule is used to supply nitrogen to the infrared spectrometer to purge the infrared spectrometer. The infrared spectrometer is used to detect the hydrogen to be tested flowing through the gas pool.

[0012] Optionally, the sample supply submodule includes a sample storage device, a sample pressure control device, and a sample flow control device connected in sequence, and the outlet of the sample flow control device is connected to any opening of the first three-way valve.

[0013] Optionally, the hydrogen supply submodule includes a hydrogen generator, a hydrogen purification device, a hydrogen pressure control device, and a first hydrogen flow control device connected in sequence, with the outlet of the first hydrogen flow control device connected to the inlet of the gas pool.

[0014] The nitrogen supply submodule includes an air compressor, a nitrogen separator, a nitrogen purification device, a nitrogen pressure control device, and a nitrogen flow control device connected in sequence. The outlet of the nitrogen flow control device is connected to the gas inlet of the infrared spectrometer.

[0015] Optionally, the gas pool is equipped with a temperature control device, a pressure detection device, and a temperature detection device; the temperature control device is used to control the temperature in the gas pool according to the detection result of the temperature detection device; the pressure detection device is used to detect the outlet pressure of the gas pool.

[0016] Optionally, the detection system further includes a reference gas preparation module, which includes a standard gas storage device, a standard gas pressure control device, a standard gas flow control submodule, a second hydrogen flow control device, and a first controller.

[0017] The outlet of the standard gas storage device is connected to the inlet of the standard gas pressure control device, the outlet of the standard gas pressure control device is connected to the inlet of the standard gas flow control submodule, and the inlet of the second hydrogen flow control device is connected to the outlet of the hydrogen supply submodule. The outlet of the standard gas flow control submodule and the outlet of the second hydrogen flow control device are connected through any two openings of a second three-way valve, and the remaining opening of the second three-way valve is connected to the inlet of the gas pool. The first controller is connected to the standard gas flow control submodule and the second hydrogen flow control device respectively, and is used to adjust the gas flow of the standard gas flow control submodule and the second hydrogen flow control device based on a preset control gas configuration ratio.

[0018] Optionally, the standard gas flow control submodule includes multiple standard gas flow control devices with different ranges, the inlets of the multiple standard gas flow control devices are connected in parallel to the outlets of the standard gas pressure control device, and the outlets of the multiple standard gas flow control devices are connected in parallel to any opening of the second three-way valve.

[0019] Optionally, the detection system further includes an exhaust gas treatment module, which includes a first hydrogen concentration sensor, an air compressor, an air flow control device, a premixing device, a catalytic conversion device, a second hydrogen concentration sensor, an exhaust gas emission valve, and a second controller.

[0020] The exhaust gas inlet of the premixing device is connected to the outlet of the gas pool, the outlet of the air compressor is connected to the inlet of the air flow control device, the outlet of the air flow control device is connected to the air inlet of the premixing device, and the outlet of the premixing device is connected to the inlet of the catalytic conversion device; the exhaust gas emission valve is located at the outlet of the catalytic conversion device, and the exhaust gas emission valve has an emission port and a circulation port, and the circulation port is connected to the circulation gas inlet of the premixing device;

[0021] The first hydrogen concentration sensor is installed at the exhaust gas inlet of the premixing device to detect the first hydrogen concentration in the exhaust gas; the catalytic conversion device is loaded with a catalyst to convert the hydrogen in the exhaust gas; the second hydrogen concentration sensor is installed between the outlet of the catalytic conversion device and the exhaust gas emission valve to detect the second hydrogen concentration in the converted exhaust gas.

[0022] The second controller is connected to the first hydrogen concentration sensor, the air flow control device, the second hydrogen concentration sensor, and the exhaust gas valve respectively. It is used to control the gas flow of the air flow control device according to the detection result of the first hydrogen concentration sensor, and to control the opening and closing of the exhaust port and the recirculation port of the exhaust gas valve according to the detection result of the second hydrogen concentration sensor.

[0023] This disclosure also provides a method for detecting trace impurities in hydrogen gas, the method comprising:

[0024] Connect the system preprocessing submodule to the detection module, perform balance preprocessing on the detection module, and purge the detection module using the external gas supply module until the detection module reaches a balanced state.

[0025] The hydrogen gas to be tested is introduced into the gas cell, and the hydrogen gas flowing through the gas cell is detected using an infrared spectrometer to obtain a detection spectrum.

[0026] Based on the preset calibration curve and the detection spectrum, the content of each trace impurity in the hydrogen gas to be tested is determined.

[0027] Optionally, when using an infrared spectrometer to detect the hydrogen gas flowing through the gas cell, the detection conditions include: a wavenumber of 4000 cm⁻¹. -1 ~650cm -1 Resolution higher than 0.5cm -1 The number of scans is higher than 64, the temperature in the gas cell is 30℃~70℃, and the pressure is 600Pa~900Pa.

[0028] Optionally, the trace impurities include at least one of formic acid, carbon monoxide, carbon dioxide, ammonia, water, methane, ethylene, ethane, and formaldehyde.

[0029] Optionally, purging the detection module using an external gas supply module includes:

[0030] The gas cell was purged with hydrogen for at least 5 minutes, and the infrared spectrometer was purged with nitrogen for at least 60 minutes; wherein...

[0031] The outlet pressure of the hydrogen gas is not less than 10 psi, and the flow rate is not less than 0.5 L / min; the outlet pressure of the nitrogen gas is not less than 10 psi, and the flow rate is not less than 0.5 L / min.

[0032] The purity of the hydrogen is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 μmol / mol, the concentration of carbon monoxide is not higher than 0.1 μmol / mol, the concentration of carbon dioxide is not higher than 0.1 μmol / mol, and the concentration of water is not higher than 2.0 μmol / mol.

[0033] The purity of the nitrogen gas is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 μmol / mol, the concentration of carbon monoxide is not higher than 0.1 μmol / mol, the concentration of carbon dioxide is not higher than 0.1 μmol / mol, and the concentration of water is not higher than 2.0 μmol / mol.

[0034] Optionally, the preset calibration curve is determined by the following method:

[0035] Hydrogen gas is mixed with a standard gas to obtain N control gases, wherein the standard gas contains at least one trace impurity of known amount, N is an integer greater than 1, and the concentration of the standard gas in the N control gases increases in a gradient.

[0036] The N samples of control gas are introduced into a gas cell, and each sample of control gas flowing through the gas cell is detected by an infrared spectrometer to obtain N control spectra.

[0037] Based on the N reference spectra and the standard gas concentrations in each reference gas, the preset calibration curve is determined.

[0038] With the above technical solution, the detection system disclosed herein is simple to operate. Using this detection system, multiple trace impurities in hydrogen can be detected simultaneously in a single test, and it has the advantages of low detection limit, high detection accuracy, and good repeatability.

[0039] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0040] 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:

[0041] Figure 1 This is a schematic diagram of the structure of the detection system disclosed herein;

[0042] Figure 2 This is the detection spectrum of hydrogen A to be tested in this embodiment of the present disclosure;

[0043] Figure 3 This is the detection spectrum of the actual sample gas G in this embodiment of the disclosure.

[0044] Explanation of reference numerals in the attached figures

[0045] 1. Detection module; 2. Sample processing module

[0046] 3. External gas supply module; 4. Reference gas preparation module

[0047] 5. Exhaust gas treatment module; 6. Temperature control device

[0048] 7. Pressure detection device; 8. Temperature detection device

[0049] 9. Sample storage device; 10. Sample pressure control device

[0050] 11 Sample flow control device 12 System pretreatment submodule

[0051] 13 First three-way valve 14 Air compression device

[0052] 15 Nitrogen separation unit 16 Nitrogen purification unit

[0053] 17 Nitrogen pressure control device 18 Nitrogen flow control device

[0054] 19 Hydrogen generator 20 Hydrogen purification unit

[0055] 21 Hydrogen pressure control device 22 First hydrogen flow control device

[0056] 23 Three-way valve 24 Standard gas storage device

[0057] 25 Standard gas pressure control device 26 Standard gas flow control device

[0058] 27 Standard gas flow control device; 28 Second hydrogen flow control device

[0059] 29 Second three-way valve 30 First controller

[0060] 31 First hydrogen concentration sensor 32 Premixing device

[0061] 33 Air compressor 34 Air flow control device

[0062] 35 Catalytic Conversion Unit 36 ​​Second Hydrogen Concentration Sensor

[0063] 37 Exhaust Gas Emission Valve Detailed Implementation

[0064] 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.

[0065] The first aspect of this disclosure provides a system for detecting trace impurities in hydrogen gas, such as... Figure 1 As shown, the detection system includes: a sample processing module 2, an external gas supply module 3, and a detection module 1. The sample processing module 2 includes a sample supply submodule, a first three-way valve 13, and a system pretreatment submodule 12. The external gas supply module 3 includes a hydrogen supply submodule and a nitrogen supply submodule. The detection module 1 includes an infrared spectrometer and a gas cell.

[0066] The sample supply submodule and the system preprocessing submodule 12 are respectively connected to any two openings of the first three-way valve 13, and the remaining opening of the first three-way valve 13 is connected to the inlet of the gas pool; the sample supply submodule is used to supply the hydrogen to be tested into the gas pool, and the system preprocessing submodule 12 is used to perform equilibration preprocessing on the detection module.

[0067] The outlet of the hydrogen supply submodule is connected to the inlet of the gas pool, and the outlet of the nitrogen supply submodule is connected to the gas inlet of the infrared spectrometer. The hydrogen supply submodule is used to supply hydrogen to the gas pool to purge the gas pool, and the nitrogen supply submodule is used to supply nitrogen to the infrared spectrometer to purge the infrared spectrometer. The infrared spectrometer is used to detect the hydrogen to be tested flowing through the gas pool.

[0068] In this disclosure, specifically, the hydrogen gas to be tested can be hydrogen gas for fuel cells; the infrared spectrometer can be a Fourier transform infrared spectrometer, which can be equipped with a high-sensitivity MCT detector with a sensitivity higher than 0.5 cm⁻¹. -1 The gas cell can be an inert gas cell with an optical path length of more than 2m.

[0069] The detection system disclosed herein is simple to operate and can simultaneously detect multiple trace impurities in hydrogen in a single test. It also has advantages such as low detection limit, high detection accuracy, and good repeatability.

[0070] According to this disclosure, the sample supply submodule may include a sample storage device 9, a sample pressure control device 10, and a sample flow control device 11 connected in sequence, wherein the outlet of the sample flow control device 11 is connected to any opening of the first three-way valve 13.

[0071] Specifically, in this disclosure, the connection between the sample supply submodule or the system pretreatment submodule and the detection module can be controlled by switching the first three-way valve. When the system pretreatment submodule is connected to the detection module, it can perform balancing pretreatment on the detection module to eliminate or weaken the adsorption effect of the detection module on strongly adsorbing impurities, thereby reducing the adsorption amount of trace impurities in the entire detection system, which helps to improve the detection accuracy of the system. The model and control accuracy of the sample pressure control device and the sample flow control device can be selected according to the actual needs of the gas cell. Preferably, the sample pressure control device can be a passivated adjustable pressure gauge, and the sample flow control device can be a mass flow meter with a passivated connector. All pipelines involved in the sample processing module can be inertized stainless steel pipelines and valves to reduce the adsorption of trace impurities, which helps to further improve the detection accuracy of the system.

[0072] According to this disclosure, the hydrogen supply submodule may include a hydrogen generator 19, a hydrogen purification device 20, a hydrogen pressure control device 21, and a first hydrogen flow control device 22 connected in sequence, with the outlet of the first hydrogen flow control device 22 connected to the inlet of the gas pool; the nitrogen supply submodule may include an air compressor 14, a nitrogen separator 15, a nitrogen purification device 16, a nitrogen pressure control device 17, and a nitrogen flow control device 18 connected in sequence, with the outlet of the nitrogen flow control device 18 connected to the gas inlet of the infrared spectrometer.

[0073] In this disclosure, specifically, the hydrogen generating device can be a pure water electrolysis device, an alkaline water electrolysis device, or a compressed hydrogen cylinder, and the hydrogen purification device can be a molecular sieve dehydration device or a metal membrane filtration hydrogen purification device; preferably, the hydrogen generating device can be a pure water electrolysis device, and the hydrogen purification device can be a multi-stage device combining a molecular sieve dehydration device and a metal membrane filtration hydrogen purification device. The purified hydrogen, after passing through a hydrogen pressure control device and a first hydrogen flow control device, enters the gas pool via a three-way valve 23 as a purging gas to stabilize the detection baseline.

[0074] The nitrogen purification device can be a molecular sieve dehydration device or other forms of purification device. The purified nitrogen enters the detection module as a purge gas to purge the detection module after passing through a nitrogen pressure control device and a nitrogen flow control device.

[0075] In the purified hydrogen or nitrogen, the purity of hydrogen or nitrogen is better than 99.9997%, the concentration of hydrocarbons, CO, and CO2 is less than 0.1 μmol / mol, the concentration of H2O is less than 2.0 μmol / mol, the outlet pressure of hydrogen or nitrogen is not less than 10 psi, and the flow rate is not less than 0.5 L / min.

[0076] According to this disclosure, the gas pool may be equipped with a temperature control device 6, a pressure detection device 7, and a temperature detection device 8; the temperature control device 6 is used to control the temperature in the gas pool according to the detection result of the temperature detection device 8; the pressure detection device 7 is used to detect the outlet pressure of the gas pool.

[0077] In this disclosure, there are no specific limitations on the types of temperature detection device, pressure detection device, and temperature control device. Preferably, the temperature detection device can be a high-precision thermocouple detector placed in the middle of the gas pool; the pressure detection device can be a high-precision pressure sensor placed at the outlet of the gas pool; and the temperature control device can be an overall heating pack for the gas pool and an electronic temperature feedback control system with a temperature control accuracy of 1°C.

[0078] According to this disclosure, the detection system may further include a reference gas preparation module 4, which may include a standard gas storage device 24, a standard gas pressure control device 25, a standard gas flow control submodule, a second hydrogen flow control device 28, and a first controller 30.

[0079] The outlet of the standard gas storage device 24 is connected to the inlet of the standard gas pressure control device 25, the outlet of the standard gas pressure control device 25 is connected to the inlet of the standard gas flow control submodule, and the inlet of the second hydrogen flow control device 28 is connected to the outlet of the hydrogen supply submodule. The outlet of the standard gas flow control submodule and the outlet of the second hydrogen flow control device 28 are connected through any two openings of the second three-way valve 29, and the remaining opening of the second three-way valve 29 is connected to the inlet of the gas pool. The first controller 30 is connected to the standard gas flow control submodule and the second hydrogen flow control device 28 respectively, and is used to adjust the gas flow of the standard gas flow control submodule and the second hydrogen flow control device 28 based on a preset control gas configuration ratio.

[0080] In this disclosure, specifically, the standard gas storage device can store standard gas containing at least one trace impurity of known amount. The first controller 30, by adjusting the gas flow rates of the standard gas flow control submodule and the second hydrogen flow control device, enables the hydrogen from the second hydrogen flow control device and the standard gas from the standard gas flow control submodule to be mixed, thereby configuring a control gas containing different concentrations of standard gas. This control gas can be used to determine a calibration curve.

[0081] According to this disclosure, the standard gas flow control submodule may include multiple standard gas flow control devices with different ranges, such as standard gas flow control device 26 and standard gas flow control device 27. The inlets of the multiple standard gas flow control devices are connected in parallel to the outlet of the standard gas pressure control device 25, and the outlets of the multiple standard gas flow control devices are connected in parallel to any opening of the second three-way valve 29.

[0082] In this disclosure, specifically, the standard gas pressure control device can be a passivated adjustable pressure gauge, and the standard gas flow control device can be a mass flow meter with passivated fittings. All pipelines involved in the control gas preparation module can be inert stainless steel pipelines and valves to reduce the adsorption of trace impurities, which helps to further improve the detection accuracy of the detection system.

[0083] According to this disclosure, the detection system may further include an exhaust gas treatment module 5, which may include a first hydrogen concentration sensor 31, an air compressor 33, an air flow control device 34, a premixing device 32, a catalytic conversion device 35, a second hydrogen concentration sensor 36, an exhaust gas emission valve 37, and a second controller.

[0084] The exhaust gas inlet of the premixing device 32 is connected to the outlet of the gas pool; the outlet of the air compressor 33 is connected to the inlet of the air flow control device 34; the outlet of the air flow control device 34 is connected to the air inlet of the premixing device 32; and the outlet of the premixing device 32 is connected to the inlet of the catalytic conversion device 35. The exhaust gas emission valve 37 is located at the outlet of the catalytic conversion device 35 and has an exhaust port and a recirculation port. The recirculation port is connected to the recirculation gas inlet of the premixing device 32.

[0085] The first hydrogen concentration sensor 31 is installed at the exhaust gas inlet of the premixing device 32 to detect the first hydrogen concentration in the exhaust gas; the catalytic conversion device 35 is loaded with a catalyst to convert the hydrogen in the exhaust gas; the second hydrogen concentration sensor 36 is installed between the outlet of the catalytic conversion device 35 and the exhaust gas emission valve 37 to detect the second hydrogen concentration in the converted exhaust gas.

[0086] The second controller is connected to the first hydrogen concentration sensor 31, the air flow control device 34, the second hydrogen concentration sensor 36, and the exhaust gas valve 37 respectively. It is used to control the gas flow of the air flow control device 34 according to the detection result of the first hydrogen concentration sensor 31, and to control the opening and closing of the exhaust port and the recirculation port of the exhaust gas valve 37 according to the detection result of the second hydrogen concentration sensor 36.

[0087] In this disclosure, specifically, the catalytic conversion device can be a single-tube reactor, or a multi-tube or microchannel reactor. The second controller can regulate the ratio of exhaust gas to air by controlling the gas flow rate of the air flow control device, ensuring that the concentration of hydrogen in the mixed gas entering the catalytic conversion device is within the explosion safety limit; the second controller can control the exhaust port of the exhaust gas valve to open when the second hydrogen concentration in the converted exhaust gas is less than a preset value, so as to discharge the converted exhaust gas to the outside; when the second hydrogen concentration in the converted exhaust gas is greater than the preset value, the controller can control the circulation port of the exhaust gas valve to open, so as to circulate the converted exhaust gas to the premixing device for catalytic conversion again, until the hydrogen concentration is less than the preset value.

[0088] The reaction temperature in the catalytic conversion device can be 50–350℃, preferably 100–250℃.

[0089] Specifically, in this disclosure, the detection system has low detection limits for each trace impurity; for example, the detection limit for formic acid is 0.04 × 10⁻⁶. -6 The detection limit for carbon monoxide is 0.04 × 10⁻⁶ mol / mol. -6 The detection limit for carbon dioxide is 0.4 × 10⁻⁶ mol / mol. -6The detection limit for methane is 0.2 × 10⁻⁶ mol / mol. -6 The detection limit for ethane is 0.2 × 10⁻⁶ mol / mol. -6 The detection limit for ethylene is 0.2 × 10⁻⁶ mol / mol. -6 The detection limit for formaldehyde is 0.02 × 10⁻⁶ mol / mol. -6 The detection limit for ammonia is 0.08 × 10⁻⁶ mol / mol. -6 mol / mol, the detection limit for water is 2 × 10⁻⁶. - 6 mol / mol.

[0090] The second aspect of this disclosure provides a method for detecting trace impurities in hydrogen gas. The method includes: connecting a system preprocessing submodule to a detection module; performing equilibration preprocessing on the detection module; and purging the detection module using an external gas supply module until the detection module reaches equilibrium; introducing the hydrogen gas to be tested into a gas cell; and detecting the hydrogen gas flowing through the gas cell using an infrared spectrometer to obtain a detection spectrum; and determining the content of each trace impurity in the hydrogen gas to be tested based on a preset calibration curve and the detection spectrum.

[0091] Optionally, when using an infrared spectrometer to detect the pretreated hydrogen gas flowing through the gas cell, the detection conditions may include: a wavenumber of 4000 cm⁻¹. -1 ~650cm -1 Resolution higher than 0.5cm -1 The number of scans is higher than 64, the temperature in the gas cell is 30℃~70℃, and the pressure is 600Pa~900Pa.

[0092] Optionally, the trace impurities may include at least one of formic acid, carbon monoxide, carbon dioxide, ammonia, water, methane, ethylene, ethane, and formaldehyde.

[0093] Optionally, purging the detection module using an external gas supply module may include: purging the gas cell with hydrogen for at least 5 minutes and purging the infrared spectrometer with nitrogen for at least 60 minutes; wherein the outlet pressure of the hydrogen is not less than 10 psi and the flow rate is not less than 0.5 L / min; the outlet pressure of the nitrogen is not less than 10 psi and the flow rate is not less than 0.5 L / min; the purity of the hydrogen is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 μmol / mol, the concentration of carbon monoxide is not higher than 0.1 μmol / mol, the concentration of carbon dioxide is not higher than 0.1 μmol / mol, and the concentration of water is not higher than 2.0 μmol / mol; the purity of the nitrogen is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 μmol / mol, the concentration of carbon monoxide is not higher than 0.1 μmol / mol, the concentration of carbon dioxide is not higher than 0.1 μmol / mol, and the concentration of water is not higher than 2.0 μmol / mol.

[0094] Optionally, the preset calibration curve can be determined by the following method: mixing hydrogen with a standard gas to obtain N portions of control gas, wherein the standard gas contains at least one trace impurity of known content, N is an integer greater than 1, and the concentration of the standard gas in the N portions of control gas increases in a gradient; allowing the N portions of control gas to enter a gas cell, and using an infrared spectrometer to detect each portion of control gas flowing through the gas cell to obtain N control spectra; and determining the preset calibration curve based on the N control spectra and the concentration of the standard gas in each control gas.

[0095] In this disclosure, specifically, the preset calibration curve can be constructed using common methods in the field. For example, the preset calibration curve can be constructed using algorithms such as PLS and CLS, which are multivariate chemometric model building tools.

[0096] The content of trace impurities in the hydrogen gas being tested can vary within a certain range. For example, the content of formic acid in the hydrogen gas being tested can be 0.04 × 10⁻⁶. -6 mol / mol~2×10 -6 The carbon monoxide content can be 0.04 × 10⁻⁶ mol / mol. -6 mol / mol~2×10 -6 The carbon dioxide content can be 0.4 × 10⁻⁶ mol / mol. -6 mol / mol~20×10 -6 The methane content can be 0.2 × 10⁻⁶ mol / mol. -6 mol / mol~20×10 -6 The ethane content can be 0.2 × 10⁻⁶ mol / mol. -6mol / mol~10×10 -6 The ethylene content can be 0.2 × 10⁻⁶ mol / mol. -6 mol / mol~20×10 -6 The formaldehyde content can be 0.02 × 10⁻⁶ mol / mol. -6 mol / mol~1×10 -6 The ammonia content can be 0.08 × 10⁻⁶ mol / mol. -6 mol / mol~10×10 -6 mol / mol, the water content can be 2×10 -6 mol / mol~25×10 -6 mol / mol.

[0097] The present disclosure is further illustrated below by means of examples, but the present disclosure is not limited thereto. Unless otherwise specified, the raw materials, reagents, instruments and equipment involved in the embodiments of the present disclosure can all be obtained by purchase.

[0098] Example 1

[0099] use Figure 1 The detection system shown uses the following method to establish a calibration curve:

[0100] (1) Five control gases were prepared using the control gas preparation module. The concentrations of each trace impurity in each control gas are shown in Table 1.

[0101] (2) Each reference gas is sequentially fed into the detection module for infrared absorption detection to obtain a reference spectrum corresponding to each reference gas. The detection conditions include: wavenumber range 4000 cm⁻¹. -1 ~650cm -1 Resolution 0.5cm -1 The number of scans was 64, the gas cell temperature was controlled at 60℃, and the pressure was controlled at 800Pa.

[0102] (3) Based on the concentration of each trace impurity in each control gas and the corresponding infrared spectrum of each trace impurity in each control gas, standard curves for formic acid, carbon monoxide, carbon dioxide, methane, ethane, ethylene, formaldehyde, ammonia and water were established by modeling using the CLS method.

[0103] Table 1

[0104] Contrast gas 1 2 3 4 5 HCOOH, pmol / mol 0.04 0.1 0.2 1 2 CO, pmol / mol 0.04 0.1 0.2 1 2 CO2, pmol / mol 0.4 1 2 10 20 CH4, pmol / mol 0.2 1 2 10 20 [C2H6, μmol / mol] 0.2 0.5 2 5 10 [C2H4, μmol / mol] 0.2 1 2 10 20 H2O, pmol / mol 2 5 10 15 25 HCHO, pmol / mol 0.02 0.1 0.2 0.5 1 [CAT, μmol / mol] 0.08 0.2 1 5 10

[0105] Example 2

[0106] use Figure 1The detection system shown uses the following method to detect the content of trace impurities in the hydrogen gas A to be tested. The actual content of each trace impurity in the hydrogen gas A to be tested is shown in Table 4:

[0107] (1) Connect the system preprocessing submodule to the detection module, perform balance preprocessing on the detection module, and purge the detection module using the external gas supply module until the detection module reaches a balanced state.

[0108] (2) The hydrogen gas A to be tested is fed into the detection module for infrared absorption detection to obtain the detection spectrum, such as... Figure 2 As shown, the detection conditions include: wavenumber range 4000 cm⁻¹ -1 ~650cm -1 Resolution 0.5cm -1 The number of scans was 64, the gas cell temperature was controlled at 60℃, and the pressure was controlled at 800Pa.

[0109] (3) Based on each detection spectrum, the detection content of each trace impurity is determined using the calibration curves obtained in Example 1, and the detection error is calculated as shown in Table 4, where the detection error = (detection content - actual content) / actual content × 100%.

[0110] Table 4

[0111] (pmol / mol) Actual content Detected content Detection error % CO 0.203 0.201 -1.01 CO2 1.962 1.914 -2.52 CH4 1.972 1.96 -0.6 [C2H4] 1.942 1.908 -1.8 [C2H6] 1.998 2.001 0.13

[0112] As can be seen from Table 4, when the detection system of this disclosure is used to simultaneously detect the content of various trace impurities in the hydrogen gas to be tested, the detection error is small, indicating that it has high detection accuracy.

[0113] Example 3

[0114] The content of trace impurities in the hydrogen gas B to be tested was determined using the method of Example 2, wherein the concentration of carbon monoxide in the hydrogen gas B to be tested was 0.20 × 10⁻⁶. -6 The concentration of carbon dioxide is 1.96 × 10⁻⁶ mol / mol. -6 The concentration of methane is 1.97 × 10⁻⁶ mol / mol. -6 The concentration of ethane is 2.0 × 10⁻⁶ mol / mol. -6 The concentration of ethylene is 1.94 × 10⁻⁶ mol / mol. -6 mol / mol. Unlike Example 2, in this example, the hydrogen gas B to be tested was detected 7 times, and the detection results are shown in Table 5.

[0115] Table 5

[0116] (pmol / mol) CO CO2 CH4 [C2H4] [C2H6] 1 0.203 1.926 1.957 1.909 2.031 2 0.203 1.919 1.971 1.907 2.033 3 0.205 1.915 1.959 1.910 2.019 4 0.201 1.912 1.968 1.906 1.970 5 0.198 1.911 1.957 1.915 1.996 6 0.199 1.910 1.956 1.905 1.981 7 0.199 1.905 1.955 1.903 1.974 Relative deviation RSD % 1.32 0.35 0.33 0.21 1.36

[0117] As can be seen from Table 5, the detection system disclosed herein has good repeatability when simultaneously detecting the content of various trace impurities in the hydrogen gas to be tested.

[0118] Example 4

[0119] The method of Example 2 was used to detect the content of trace impurities in hydrogen gas C to F, wherein hydrogen gas C contained impurities with a concentration of 0.20 × 10⁻⁶. -6 Formic acid at a concentration of mol / mol is present in the hydrogen gas D to be tested, with a concentration of 0.19 × 10⁻⁶ mol / mol. -6 The concentration of formaldehyde in the test gas E is 0.10 × 10 mol / mol. -6 The concentration of ammonia in the tested hydrogen gas F is 4.28 × 10⁻⁶ mol / mol. - 6 mol / mol water. Unlike Example 2, in this example, the trace impurity content in hydrogen C to F was first detected once to verify the accuracy, and then the trace impurity content in hydrogen C to F was detected seven times to verify the repeatability. The detection results are shown in Tables 6 and 7.

[0120] Table 6

[0121] Hydrogen to be measured (pmol / mol) Actual content Detected content Relative error % C HCOOH 0.201 0.202 0.36 E [CAT] 0.101 0.097 -4.37 F H2O 4.287 4.482 4.34 D HCHO 0.189 0.193 2.16

[0122] Table 7

[0123] Hydrogen to be measured C E F D (pmol / mol) HCOOH [CAT] H2O HCHO 1 0.203 0.093 4.240 0.193 2 0.197 0.105 4.243 0.190 3 0.204 0.093 4.254 0.199 4 0.204 0.095 4.642 0.201 5 0.199 0.095 4.690 0.185 6 0.204 0.093 4.657 0.188 7 0.205 0.104 4.647 0.196 Relative deviation RSD % 1.56 5.41 4.94 2.98

[0124] As can be seen from Table 6, when using the detection system of this disclosure to detect the content of a trace impurity in the hydrogen gas to be tested, the detection error is small, indicating that it has high detection accuracy.

[0125] As can be seen from Table 7, the detection system disclosed herein has good repeatability when detecting the content of a trace impurity in hydrogen gas alone.

[0126] Example 5

[0127] The content of trace impurities in actual sample gas G from industrial hydrogen production via hydrolysis was detected using the method described in Example 2. The detection chromatogram is shown below. Figure 3 As shown in Table 8, the test results are as follows.

[0128] Table 8

[0129] Serial number Trace impurity Content / (pmol / mol) 1 HCOOH <0.04 2 CO <0.04 3 CO2 <0.4 4 [CAT] <0.08 5 H2O 3.29 6 HCHO <0.02 7 CH4 <0.2 8 [C2H4] <0.2 9 [C2H6] <0.2

[0130] As can be seen from Table 8, the detection system disclosed herein can accurately detect the content of various trace impurities in hydrogen in a single test, and the test results meet the limit requirements of ISO 14687-19.

[0131] 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.

[0132] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0133] 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 method for detecting trace impurities in hydrogen gas, characterized in that, The detection system used in the detection method includes: a sample processing module, an external gas supply module, and a detection module. The sample processing module includes a sample supply submodule, a first three-way valve, and a system pretreatment submodule. The external gas supply module includes a hydrogen supply submodule and a nitrogen supply submodule. The detection module includes an infrared spectrometer and a gas cell. The sample supply submodule and the system preprocessing submodule are respectively connected to any two openings of the first three-way valve, and the remaining opening of the first three-way valve is connected to the inlet of the gas pool; the sample supply submodule is used to supply the hydrogen to be tested into the gas pool, and the system preprocessing submodule is used to perform equilibration preprocessing on the detection module. The outlet of the hydrogen supply submodule is connected to the inlet of the gas pool, and the outlet of the nitrogen supply submodule is connected to the gas inlet of the infrared spectrometer. The hydrogen supply submodule is used to supply hydrogen to the gas pool to purge the gas pool, and the nitrogen supply submodule is used to supply nitrogen to the infrared spectrometer to purge the infrared spectrometer. The infrared spectrometer is used to detect the hydrogen to be tested flowing through the gas pool. The hydrogen supply submodule includes a hydrogen generator, a hydrogen purification device, a hydrogen pressure control device, and a first hydrogen flow control device connected in sequence. The outlet of the first hydrogen flow control device is connected to the inlet of the gas pool. The detection system also includes a reference gas preparation module, which includes a standard gas storage device, a standard gas pressure control device, a standard gas flow control submodule, a second hydrogen flow control device, and a first controller. The detection method includes: The system preprocessing submodule is connected to the detection module to perform equilibration preprocessing on the detection module, so as to eliminate or weaken the adsorption effect of the detection module on strongly adsorbed impurities, thereby reducing the adsorption amount of trace impurities in the entire detection system; and the detection module is purged using an external gas supply module, including: purging the gas cell with hydrogen for at least 5 minutes and purging the infrared spectrometer with nitrogen for at least 60 minutes, until the detection module reaches an equilibrium state. The hydrogen gas to be tested is introduced into a gas cell, and the hydrogen gas flowing through the gas cell is detected using an infrared spectrometer to obtain a detection spectrum; the trace impurities include at least one of formic acid, carbon monoxide, carbon dioxide, ammonia, water, methane, ethylene, ethane and formaldehyde; Based on the preset calibration curve and the detection spectrum, the content of each trace impurity in the hydrogen gas to be tested is determined.

2. The detection method according to claim 1, characterized in that, The sample supply submodule includes a sample storage device, a sample pressure control device, and a sample flow control device connected in sequence, and the outlet of the sample flow control device is connected to any opening of the first three-way valve.

3. The detection method according to claim 1, characterized in that, The nitrogen supply submodule includes an air compressor, a nitrogen separator, a nitrogen purification device, a nitrogen pressure control device, and a nitrogen flow control device connected in sequence. The outlet of the nitrogen flow control device is connected to the gas inlet of the infrared spectrometer.

4. The detection method according to claim 1, characterized in that, The gas pool is equipped with a temperature control device, a pressure detection device, and a temperature detection device; the temperature control device is used to control the temperature inside the gas pool based on the detection results of the temperature detection device; the pressure detection device is used to detect the outlet pressure of the gas pool.

5. The detection method according to any one of claims 1 to 4, characterized in that, The outlet of the standard gas storage device is connected to the inlet of the standard gas pressure control device, the outlet of the standard gas pressure control device is connected to the inlet of the standard gas flow control submodule, and the inlet of the second hydrogen flow control device is connected to the outlet of the hydrogen supply submodule. The outlet of the standard gas flow control submodule and the outlet of the second hydrogen flow control device are connected through any two openings of a second three-way valve, and the remaining opening of the second three-way valve is connected to the inlet of the gas pool. The first controller is connected to the standard gas flow control submodule and the second hydrogen flow control device respectively, and is used to adjust the gas flow of the standard gas flow control submodule and the second hydrogen flow control device based on a preset control gas configuration ratio.

6. The detection method according to claim 5, characterized in that, The standard gas flow control submodule includes multiple standard gas flow control devices with different ranges. The inlets of the multiple standard gas flow control devices are connected in parallel to the outlets of the standard gas pressure control devices, and the outlets of the multiple standard gas flow control devices are connected in parallel to any opening of the second three-way valve.

7. The detection method according to any one of claims 1 to 4, characterized in that, The detection system also includes an exhaust gas treatment module, which includes a first hydrogen concentration sensor, an air compressor, an air flow control device, a premixing device, a catalytic conversion device, a second hydrogen concentration sensor, an exhaust gas emission valve, and a second controller. The exhaust gas inlet of the premixing device is connected to the outlet of the gas pool, the outlet of the air compressor is connected to the inlet of the air flow control device, the outlet of the air flow control device is connected to the air inlet of the premixing device, and the outlet of the premixing device is connected to the inlet of the catalytic conversion device; the exhaust gas emission valve is located at the outlet of the catalytic conversion device, and the exhaust gas emission valve has an emission port and a circulation port, and the circulation port is connected to the circulation gas inlet of the premixing device; The first hydrogen concentration sensor is installed at the exhaust gas inlet of the premixing device to detect the first hydrogen concentration in the exhaust gas; the catalytic conversion device is loaded with a catalyst to convert the hydrogen in the exhaust gas; the second hydrogen concentration sensor is installed between the outlet of the catalytic conversion device and the exhaust gas emission valve to detect the second hydrogen concentration in the converted exhaust gas. The second controller is connected to the first hydrogen concentration sensor, the air flow control device, the second hydrogen concentration sensor, and the exhaust gas valve respectively. It is used to control the gas flow of the air flow control device according to the detection result of the first hydrogen concentration sensor, and to control the opening and closing of the exhaust port and the recirculation port of the exhaust gas valve according to the detection result of the second hydrogen concentration sensor.

8. The detection method according to claim 1, characterized in that, When using an infrared spectrometer to detect the hydrogen gas flowing through the gas cell, the detection conditions include: a wavenumber of 4000 cm⁻¹. -1 ~650cm -1 Resolution higher than 0.5 cm -1 The number of scans is higher than 64, the temperature in the gas cell is 30℃~70℃, and the pressure is 600Pa~900Pa.

9. The detection method according to claim 1, characterized in that, During the purging of the detection module using an external gas supply module, The outlet pressure of the hydrogen gas is not less than 10 psi, and the flow rate is not less than 0.5 L / min; the outlet pressure of the nitrogen gas is not less than 10 psi, and the flow rate is not less than 0.5 L / min. The purity of the hydrogen is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 µmol / mol, the concentration of carbon monoxide is not higher than 0.1 µmol / mol, the concentration of carbon dioxide is not higher than 0.1 µmol / mol, and the concentration of water is not higher than 2.0 µmol / mol. The purity of the nitrogen gas is not less than 99.9997%, the concentration of hydrocarbons is not higher than 0.1 µmol / mol, the concentration of carbon monoxide is not higher than 0.1 µmol / mol, the concentration of carbon dioxide is not higher than 0.1 µmol / mol, and the concentration of water is not higher than 2.0 µmol / mol.

10. The detection method according to claim 1, characterized in that, The preset calibration curve is determined by the following method: Hydrogen gas is mixed with a standard gas to obtain N control gases, wherein the standard gas contains at least one trace impurity of known amount, N is an integer greater than 1, and the concentration of the standard gas in the N control gases increases in a gradient. The N samples of control gas are introduced into a gas cell, and each sample of control gas flowing through the gas cell is detected by an infrared spectrometer to obtain N control spectra. Based on the N reference spectra and the standard gas concentrations in each reference gas, the preset calibration curve is determined.

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