System and method for measuring trace impurity concentration in hydrogen gas

Abstract

The present invention relates to a system and method for measuring the concentration of trace impurities in hydrogen, wherein the trace impurities include one or more of sulfur-containing compounds, formaldehyde and formic acid, and the system includes: a gas concentration unit, including a capture device and a gas collection and metering device, for low-temperature capture and high-temperature release of trace impurities in a preset volume of hydrogen to be measured by the capture device, and collecting and metering the preset volume of hydrogen to be measured by the gas collection and metering device; a gas detection unit, which is connected to the gas concentration unit in an openable and closable manner, and is used to detect trace impurities obtained by high-temperature release. The system of the present invention can accurately measure the concentration of trace impurities in hydrogen for fuel cell vehicles with a single injection, and the method of the present invention is simple in process and has high measurement accuracy and reliability.

Description

Technical Field

[0001] The present invention relates to a system and method for measuring the concentration of trace impurities in hydrogen. Background Art

[0002] As a secondary energy source, hydrogen energy has multiple advantages such as diverse sources, zero terminal emissions, and a wide range of uses. It is one of my country's important national strategic emerging industries, and fuel cell vehicles (FCVs) are one of the important carriers of hydrogen energy. FCVs are electric vehicles that use hydrogen to release electricity through electrochemical catalytic conversion inside a fuel cell (with proton exchange membrane PEMFC as the core component), and then use electricity to drive the vehicle. The hydrogen used in FCVs is different from the hydrogen used in petrochemical refineries. In addition to certain requirements for hydrogen purity, it is also required to control the content of trace impurities in hydrogen that affect battery performance and life. Foreign studies have shown that even 0.01×10 -9 mol / mol sulfur compounds can also cause irreversible decline in fuel cell performance. The presence of trace amounts of formaldehyde and formic acid can also seriously affect fuel cell power performance. Therefore, in order to ensure the quality of hydrogen for FCV, the country formulated GB / T37244 "Hydrogen for Proton Exchange Membrane Fuel Cell Vehicles" in 2018. The standard gives clear descriptions of the types and contents of 13 impurities that affect battery performance. Among them, sulfur compounds, formaldehyde and formic acid are the three parameters with more stringent limit requirements, requiring sulfur compounds <0.004×10 -6 mol / mol, formaldehyde <0.01×10 -6 mol / mol, formic acid <0.2×10 -6 mol / mol.

[0003] Since the control limit requirement is extremely low, the detection technology capability is very high. At present, in the field of sulfide analysis in the air, the gas chromatography / sulfur chemiluminescence detector technology is mostly used in China. The detection limit of the single-component sulfur-containing compound is 10×10 -9 mol / mol, which cannot meet the index requirements for sulfur compounds in FCV hydrogen. The existing formaldehyde detection in ambient air in China adopts GB / T 16129 "Standard Method for Sanitary Inspection of Formaldehyde in Atmosphere of Residential Areas - Spectrophotometric Method". This method requires pre-absorption of the sample, a large amount of sample collection, and the use of sulfuric acid and other reagents, making the determination process cumbersome. Formic acid detection mostly adopts HJ 1004-2018 "Ion Chromatography Method for Determination of Organic Acids (Acetic Acid, Formic Acid and Oxalic Acid) in Ambient Air Precipitation"; GB / T17068-1997 "Gas Chromatographic Determination of Formic Acid in Workshop Air" and so on. The detection adopts silicone tube collection, acid solution adsorption and re-esterification, and then gas chromatography analysis. At present, there is no method in the field of formic acid analysis in ambient air in China that can meet the FCV hydrogen limit requirements.

[0004] There is currently no measurement in China. -12 mol / mol level of sulfur-containing compounds analysis instruments and methods, nor the use of gas chromatography to determine the 10 -9 The analysis method of formaldehyde and formic acid at the mol / mol level. Foreign solutions require multiple analytical instruments with auxiliary equipment to complete, and none of them can complete the analysis of sulfur compounds, formaldehyde and formic acid in FCV hydrogen samples through a single injection. Summary of the invention

[0005] The purpose of the present invention is to provide a system and method for measuring the concentration of trace impurities in hydrogen. The system of the present invention can accurately measure the concentration of trace impurities in hydrogen for fuel cell vehicles with a single injection. The method of the present invention has a simple process and high measurement accuracy and reliability.

[0006] In order to achieve the above object, the first aspect of the present invention provides a system for measuring the concentration of trace impurities in hydrogen, wherein the trace impurities include one or more of sulfur-containing compounds, formaldehyde and formic acid, and the system comprises:

[0007] A gas concentration unit, comprising a capture device and a gas collecting and metering device, for performing low-temperature capture and high-temperature release of the trace impurities in a preset volume of hydrogen to be measured by the capture device, and for collecting and metering the preset volume of hydrogen to be measured by the gas collecting and metering device;

[0008] The gas detection unit is in openable and closable gas communication with the gas concentration unit, and is used for detecting the trace impurities obtained by the high-temperature release.

[0009] The second aspect of the present invention provides a method for measuring the concentration of trace impurities in hydrogen using the system provided by the first aspect of the present invention, the method comprising:

[0010] The temperature of the capture device is set at -180°C to -150°C, the preset volume of the hydrogen to be measured is introduced into the gas concentration unit, the hydrogen to be measured flows through the capture device to capture trace impurities in the hydrogen to be measured, and the preset volume of the hydrogen to be measured is introduced into the gas collection and metering device for metering;

[0011] The temperature of the capture device is set at 60-100° C. to release the trace impurities and obtain a gas mixture;

[0012] The gas mixture carried by the carrier gas is introduced into the gas detection unit for detection.

[0013] Through the above technical solution, the system of the present invention has a structure combining a gas concentration unit and a gas detection unit, which can accurately measure the content of trace impurities such as sulfur compounds, formaldehyde, and formic acid in hydrogen with a single injection.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0016] Figure 1 It is a structural schematic diagram of a specific implementation mode of the system of the present invention;

[0017] Figure 2 is a spectrum obtained by detecting the sample of Example 1 of the present invention through a sulfur chemiluminescence detector;

[0018] Figure 3 This is the mass spectrum of the sample of Example 1 of the present invention detected by a mass spectrometer.

[0019] Description of Reference Numerals

[0020] 1Gas Concentration Unit 2Gas Detection Unit 3Injector

[0021] 4 trap 5 metering tank 6 liquid nitrogen refrigerator

[0022] 7 Heater 8 Pump 9 Inertization two-way

[0023] 10 non-polar chromatographic column 11 second damping column 12 first damping column

[0024] 13 Sulfur chemiluminescence detector 14 Mass spectrometer detector 15 Microplate flow splitter

[0025] 16 Sample transfer line 17 Injection line 18 Carrier gas line

[0026] 19 Fourth pipeline 20 Third pipeline 21 First pipeline

[0027] 22 Second pipeline 23 Fifth pipeline

[0028] 31 first interface 32 second interface 33 third interface

[0029] 34 fourth interface 35 fifth interface 36 sixth interface DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0031] A first aspect of the present invention provides a system for measuring the concentration of trace impurities in hydrogen, wherein the trace impurities include one or more of sulfur-containing compounds, formaldehyde and formic acid, and the system includes: a gas concentration unit 1, including a capture device and a gas collection and metering device, for low-temperature capture and high-temperature release of the trace impurities in a preset volume of hydrogen to be measured by the capture device, and collecting and metering the preset volume of hydrogen to be measured by the gas collection and metering device; a gas detection unit 2, which is gas-connected to the gas concentration unit 1 in an openable and closable manner, and is used to detect the trace impurities obtained by the high-temperature release.

[0032] The preset volume of hydrogen to be tested in the present invention refers to the hydrogen to be tested after impurities are removed. Since the content of impurities in the hydrogen to be tested is very low, the preset volume of hydrogen to be tested is approximately equal to the hydrogen to be tested without removing impurities. The system of the present invention has a structure combining a gas concentration unit and a gas detection unit. The gas concentration unit can capture and release trace impurities in the hydrogen to be tested, thereby effectively separating the hydrogen and trace impurities in the sample to be tested. The gas detection unit further detects the concentration of trace impurities, and has the advantage of accurately measuring the content of trace impurities in hydrogen with one injection.

[0033] In a specific embodiment, Figure 1 As shown, the capture device includes a capture trap 4 and a temperature control device, and the temperature control device is used to control the temperature of the capture trap 4.

[0034] In a preferred embodiment, the trap is a stainless steel pipeline that has been inertized to reduce the adsorption of components caused during the release of trace impurities, which is conducive to further improving the accuracy and reliability of the measurement of the system of the present invention. In another preferred specific embodiment, the temperature control device includes a liquid nitrogen refrigerator 6 and a heater 7. The liquid nitrogen refrigerator can reduce the temperature of the trap to a preset temperature, effectively capturing impurities without capturing hydrogen, and the heater can increase the temperature of the trap to release the captured trace impurities. The present invention does not specifically limit the types of liquid nitrogen refrigerators and heaters. Preferably, the liquid nitrogen refrigerator is a refrigerator that can control the injection of liquid nitrogen, and the heater is a heater with a heating wire.

[0035] In one embodiment, Figure 1As shown, the gas concentration unit 1 further includes an injector 3; the injector includes a sample inlet, a sample outlet, a carrier gas inlet and a carrier gas outlet, the sample outlet is connected to the inlet of the trap 4, the outlet of the trap 4 can be switched to be connected to the inlet of the gas detection unit 2 or to the inlet of the gas collection and metering device; the carrier gas outlet can be switched to be connected to or not connected to the inlet of the trap 4. Preferably, when the outlet of the trap 4 is connected to the inlet of the gas detection unit 2, the carrier gas outlet is connected to the inlet of the trap 4; when the outlet of the trap 4 is connected to the inlet of the gas collection and metering device, the carrier gas outlet is not connected to the inlet of the trap 4.

[0036] In one embodiment, the gas detection unit 2 includes a non-polar chromatographic column 10, a microplate flow splitter 15, a first detection channel and a second detection channel, wherein the first detection channel includes a first damping column 12 and a mass spectrometer detector 14; the second detection channel includes a second damping column 11 and a sulfur chemiluminescence detector 13; the inlet of the non-polar chromatographic column 10 is connected to the inlet of the gas detection unit 2, the outlet of the non-polar chromatographic column 10 is connected to the inlet of the microplate flow splitter 15, the first outlet of the microplate flow splitter 15 is connected to the inlet of the first detection channel, and the second outlet of the microplate flow splitter 15 is connected to the inlet of the second detection channel. According to the present invention, the microplate flow splitter is preferably an inertized splitter, which can split the components flowing out of a single chromatographic column into two detectors on the same chromatogram, and can detect different target analytes on different detectors. The sulfur chemiluminescence detector only responds to the presence of sulfur-containing compounds in the sample. The gas detection unit in the system of the present invention can accurately detect the concentration of trace impurities.

[0037] According to the present invention, non-polar chromatographic columns are well known to those skilled in the art. In a specific embodiment, the stationary phase of the non-polar chromatographic column 10 is dimethylpolysiloxane, and the column length and inner diameter can vary within a large range, preferably the column length is 70-105m, and the inner diameter is 0.32-0.53mm. The first damping column and the second damping column are also well known to those skilled in the art. In an embodiment, the first damping column 12 and the second damping column 11 are each independently an elastic quartz chromatographic column, and there is no specific restriction on the material thereof, for example, it can be deactivated quartz; the first damping column 12 and the second damping column 11 are each independently filled with particulate matter, which is conventionally used in damping columns. The column length and inner diameter of the first damping column 12 and the second damping column 11 can also vary within a large range, preferably the column length is 1-2m, the inner diameter is 0.10-0.18mm, and the inner diameter is preferably 0.12mm, 0.15mm, and the inner diameter and column length of the damping column are matched.

[0038] In a preferred specific embodiment, the injector 3 is a six-way switching valve; the six-way switching valve includes a first interface 31, a second interface 32, a third interface 33, a fourth interface 34, a fifth interface 35 and a sixth interface 36; the first interface 31 is connected to the inlet of the gas collection and metering device, the second interface 32 is connected to the outlet of the capture trap 4, preferably the second interface 32 is connected to the outlet of the capture trap 4 through the fifth pipeline 23, the third interface 33 is connected to the inlet of the gas detection unit 2, the fifth interface 35 is connected to the inlet of the capture trap 4, preferably the fifth interface 35 is connected to the inlet of the capture trap through the fourth pipeline 19, the fourth interface 34 is formed as the carrier gas inlet, preferably the carrier gas pipeline 18 is connected to the fourth interface, the fifth interface 35 is formed as the sample outlet or the carrier gas outlet, the sixth interface 36 is formed as the sample inlet, preferably the injection pipeline 17 is connected to the sixth interface 36.

[0039] According to the present invention, the six-way switching valve has a closed state and an open state. Figure 1 As shown, the six-way switching valve is divided into two paths according to the dotted line and the solid line. The six-way switching valve is in a closed state at the solid line, and is in an open state at the dotted line; in the closed state, the fourth interface 34 is connected to the third interface 33, and the fifth interface 35 is connected to the sixth interface 36, so that the sample inlet is connected to the inlet of the capture trap 4, and the first interface 31 is connected to the second interface 32, so that the inlet of the gas collection and metering device is connected to the outlet of the capture trap 4; in the open state, the fourth interface 34 is connected to the fifth interface 35, so that the carrier gas inlet is connected to the inlet of the capture trap 4, and the second interface 32 is connected to the third interface 33, so that the outlet of the capture trap 4 is connected to the inlet of the gas detection unit 2.

[0040] In a specific embodiment of the present invention, Figure 1 As shown, the gas collection and metering device includes a pump 8 and a metering tank 5; the gas inlet of the pump 8 is connected to the inlet of the metering tank 5 through the first pipeline 21 and the second pipeline 22, and the inlet of the metering tank 5 is connected to the first interface 31 through the second pipeline 22 and the third pipeline 20; the first pipeline 21 is provided with a first control valve, the second pipeline 22 is provided with a second control valve, and the third pipeline (20) is provided with a third control valve. The first control valve, the second control valve and the third control valve are conventionally used by technicians in this field, for example, they can be gate valves, ball valves, etc., and are not limited here. In the system of the present invention, a preset volume of hydrogen is allowed to enter the metering tank through a pump, and the volume of hydrogen can be measured, which is conducive to helping to realize the detection of trace impurity concentration in the hydrogen to be measured.

[0041] In a specific embodiment, Figure 1 As shown, the gas concentration unit 1 also includes a sample transmission pipeline 16, and the gas detection unit 2 also includes an inert treatment two-way 9; the third interface 33 is connected to the inlet of the sample transmission pipeline 16, the outlet of the sample transmission pipeline 16 is connected to the inlet of the inert treatment two-way 9, and the outlet of the inert treatment two-way 9 is connected to the inlet of the non-polar chromatographic column 10.

[0042] According to the present invention, the detection limit of the system of the present invention for sulfur-containing compounds is 0.01×10 -9 mol / mol, the detection limit of formaldehyde is 1×10 -9 mol / mol, and the detection limit for formic acid is 0.1×10 -6 mol / mol, the system of the present invention is particularly suitable for detecting the concentration of ultra-low impurities in samples.

[0043] The second aspect of the present invention provides a method for measuring the concentration of trace impurities in hydrogen using the system provided by the first aspect of the present invention, the method comprising: setting the temperature of the capture device to -180°C to -150°C, introducing the preset volume of hydrogen to be measured into the gas concentration unit 1, allowing the hydrogen to be measured to flow through the capture device to capture trace impurities in the hydrogen to be measured, and introducing the preset volume of hydrogen to be measured into the gas collection and metering device for metering; setting the temperature of the capture device to 60-100°C to release the trace impurities to obtain a gas mixture; and introducing the gas mixture carried by the carrier gas into the gas detection unit 2 for detection.

[0044] According to the present invention, the introduction of the gas mixture carried by the carrier gas into the gas detection unit 2 for detection includes: passing the gas mixture carried by the carrier gas through the non-polar chromatographic column 10 and the microplate flow path splitter 15 in sequence to obtain a first outflow component and a second outflow component; allowing the first outflow component to enter the mass spectrometer detector 14 for a first detection to detect formic acid and formaldehyde; allowing the second outflow component to enter the sulfur chemiluminescence detector 13 for a second detection to detect sulfur-containing compounds. Among them, the flow rate of the first outflow component is exactly the same as the composition of the second outflow component, and the flow rates are the same or different. The method of the present invention can detect the content of trace impurities in a sample with a single injection.

[0045] In order to accurately detect trace impurities, in a specific embodiment of the present invention, the conditions for the first detection include: the ion source temperature is 200-300°C, preferably 230°C, the quadrupole temperature is 100-200°C, preferably 150°C, the EI ion source voltage is 5-240eV, preferably 70eV, and the interface temperature is 200-400°C, preferably 250°C; the conditions for the second detection include: the typical temperature of the burner is 800-850°C, preferably 800°C, the pressure of the dual plasma controller is 40-53.3kPa, H 2 The flow rate of the ozone reaction tank is 40-50 mL / min, the flow rate of the oxidant gas is 50-55 mL / min, and the pressure of the ozone reaction tank is 0.67-1.33 kPa.

[0046] In a preferred specific embodiment of the present invention, the method of the present invention includes: setting the temperature of the capture trap 4 to -180°C to -150°C, setting the six-way switching valve in a closed state, connecting the sample inlet with the inlet of the capture trap 4 so that the hydrogen to be measured enters the capture trap 4, and the trace impurities in the hydrogen to be measured are captured at low temperature, connecting the inlet of the gas collection and metering device with the outlet of the capture trap 4, so that a preset volume of hydrogen to be measured enters the gas collection and metering device for metering; setting the temperature of the capture trap 4 to 60-100°C to release the trace impurities and obtain a gas mixture; setting the six-way switching valve in an open state, connecting the carrier gas inlet with the inlet of the capture trap 4, and connecting the outlet of the capture trap 4 with the inlet of the gas detection unit 2, so that the carrier gas enters the capture trap 4 and carries the gas mixture into the gas detection unit 2 for detection.

[0047] In one embodiment of the present invention, a temperature control device is used to control the temperature of the capture trap 4. When the temperature of the capture trap needs to be lowered to capture trace impurities, the heater 7 of the temperature control device is turned off and the liquid nitrogen refrigerator 6 is turned on to lower the temperature of the capture trap; when the temperature of the capture trap needs to be increased to release the captured trace impurities, the liquid nitrogen refrigerator 6 of the temperature control device is turned off and the heater 7 is turned on to increase the temperature of the capture trap.

[0048] According to the present invention, the content of sulfur-containing compounds in the hydrogen to be measured is 0.01×10 -9 mol / mol-10×10 - 9 mol / mol, the formaldehyde content is 1×10 -9 mol / mol-20×10 -9 mol / mol, the content of formic acid is 0.1×10 -6 mol / mol-1×10 -6mol / mol; the hydrogen to be tested is hydrogen for fuel cell vehicles.

[0049] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0050] Example 1

[0051] The structure of the system of this embodiment is as follows:

[0052] like Figure 1 As shown, the system for measuring the concentration of trace impurities in hydrogen includes a gas concentration unit 1 and a gas detection unit 2 .

[0053] The gas concentration unit 1 includes a sample transmission pipeline 16, a six-way switching valve, a capture device and a gas collection and metering device, the capture device includes a capture trap 4 (an inertized stainless steel tube with an outer diameter of 1 / 16 inches, a length of 4 cm, and an inner diameter of 0.5 mm), a liquid nitrogen refrigerator 6 and a heater 7, and the gas collection and metering device includes a pump 8 and a metering tank 5 (with a volume of 1 L), and the gas inlet of the pump 8 is connected to the inlet of the metering tank 5 through a first pipeline 21 and a second pipeline 22, wherein a first control valve is provided on the first pipeline 21, a second control valve is provided on the second pipeline 22, and a third control valve is provided on the third pipeline 20;

[0054] Among them, the six-way switching valve includes a first interface 31, a second interface 32, a third interface 33, a fourth interface 34, a fifth interface 35 and a sixth interface 36. The first interface 31 is connected to the inlet of the metering tank through the second pipeline 22 and the third pipeline 20, the second interface 32 is connected to the outlet of the capture trap 4 through the fifth pipeline 23, the third interface 33 is connected to the inlet of the sample transmission pipeline, the fifth interface 35 is connected to the inlet of the capture trap 4 through the fourth pipeline 19, the fourth interface 34 is the carrier gas inlet, the carrier gas line 18 is connected to the fourth interface, the fifth interface 35 is the sample outlet or the carrier gas outlet, and the injection line 17 is connected to the sixth interface 36.

[0055] The gas detection unit 2 includes an inertized two-way pipe 9, a non-polar chromatographic column 10 (DB-1 capillary column, column length 105m, column inner diameter 0.53mm, stationary phase is dimethyl polysiloxane), a microplate flow path splitter 15, a first detection channel and a second detection channel, the first detection channel includes a first damping column 12 (a deactivated quartz column filled with particles, column length 1m, column inner diameter 0.18mm) and a mass spectrometer detector 14; the second detection channel includes a second damping column 11 (a deactivated quartz column filled with particles, column length 1m, column inner diameter 0.18mm) and a mass spectrometer detector 14. The column inner diameter is 0.18mm) and a sulfur chemiluminescence detector 13; the inlet of the inert treatment two-way is the inlet of the gas detection unit 2, the inlet of the non-polar chromatographic column 10 is connected to the outlet of the inert treatment two-way 9, the inlet of the inert treatment two-way 9 is connected to the outlet of the sample transmission pipeline 16, the outlet of the non-polar chromatographic column 10 is connected to the inlet of the microplate flow path splitter 15, the first outlet of the microplate flow path splitter 15 is connected to the inlet of the first detection channel, and the second outlet of the microplate flow path splitter 15 is connected to the inlet of the second detection channel.

[0056] The method for measuring the concentration of trace impurities in the gas sample to be tested is as follows:

[0057] First, the gas sample A to be tested is concentrated: the third control valve is closed, the first control valve and the second control valve are opened, and after the pump 8 evacuates the metering tank 5, the third control valve is opened, the first control valve is closed and the second control valve is kept open, and the six-way switching valve is placed in a closed state. The detection system introduces the hydrogen to be tested into the trap 4 through the sixth interface 36, the fifth interface 35 and the fourth pipeline 19 via the injection pipeline 17. The trap 4 is in a low temperature state (temperature is -150°C) under the action of the liquid nitrogen refrigerator to capture sulfur compounds, formaldehyde and formic acid in the hydrogen to be tested. The preset volume of hydrogen is filled into the metering tank 5 via the fifth pipeline 23, the second interface 32, the first interface 31, the third pipeline 20 and the second pipeline 22. At the same time, the carrier gas is introduced into the gas detection unit 2 via the carrier gas pipeline 18 through the fourth interface 34, the third interface 33 and the sample transmission pipeline 16;

[0058] Then the impurity concentration is detected: the six-way switching valve is placed in the open state and the heater 7 is started. The trap 4 is in a high temperature state (temperature is 80°C) under the action of the heater, and sulfur-containing compounds, formaldehyde and formic acid are released. The carrier gas enters the trap 4 through the carrier gas pipeline, the fourth interface 34, the fifth interface 35 and the fourth pipeline 19, carrying the released mixed gas containing sulfur-containing compounds, formaldehyde and formic acid, and is introduced into the gas concentration detection unit through the sample transmission pipeline 16 through the fifth pipeline 23, the second interface 32 and the third interface 33. In the gas concentration detection unit, the mixed gas enters the microplate flow path splitter through two passes after inert treatment, and is divided into a first outflow component and a second outflow component. The first outflow component enters the mass spectrometer detector 14 through the first damping column for the first detection, and the second outflow component enters the sulfur chemiluminescence detector 13 through the second damping column for the second detection. The detection conditions are shown in Table 1, and the obtained spectrum is shown in Figure 2 and Figure 3 shown.

[0059] After all components in the gas sample A are detected, the contents of each sulfur-containing compound, formaldehyde and formic acid in the gas sample A can be calculated by the external standard method. The actual content and calculated content of impurities in the gas sample A are shown in Table 2, wherein the relative error = (calculated impurity content - actual impurity content) / actual impurity content × 100%.

[0060] Table 1

[0061]

[0062]

[0063] Table 2

[0064] Actual content, mol / mol Calculated content, mol / mol Relative error, % Sulfur compounds <![CDATA[0.5×10 -9 ]]> <![CDATA[0.503×10 -9 ]]> 0.6 formaldehyde <![CDATA[12.5×10 -9 ]]> <![CDATA[12.72×10 -9 ]]> 1.8 Formic acid <![CDATA[0.8×10 -6 ]]> <![CDATA[0.81×10 -6 ]]> 1.3

[0065] Example 2

[0066] The concentration of hydrogen sulfide is 0.2×10 -9 mol / mol, formaldehyde concentration is 5×10 -9 mol / mol, formic acid concentration is 0.2×10 -6 The repeatability of the gas sample B with a concentration of mol / mol was investigated, and the results are shown in Table 3.

[0067] Table 3

[0068]

[0069]

[0070] It can be seen from the above that the system of the present invention can detect the content of trace impurities in hydrogen more accurately with one injection, and the detection result is accurate, highly reliable and repeatable.

[0071] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0072] 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, the present invention will not further describe various possible combinations.

[0073] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A system for measuring the concentration of trace impurities in hydrogen, wherein the trace impurities include one or more of sulfur-containing compounds, formaldehyde and formic acid, the system comprising: A gas concentration unit (1) comprises a capture device and a gas collecting and metering device, which is used to capture the trace impurities in a preset volume of hydrogen to be tested at low temperature and release them at high temperature through the capture device, and to collect and meter the preset volume of hydrogen to be tested through the gas collecting and metering device; A gas detection unit (2) is in openable and closable gas communication with the gas concentration unit (1), and is used to detect the trace impurities obtained by the high-temperature release; The capture device comprises a capture trap (4) and a temperature control device, wherein the temperature control device is used to control the temperature of the capture trap (4); The gas concentration unit (1) further comprises an injector (3); the injector comprises a sample inlet, a sample outlet, a carrier gas inlet and a carrier gas outlet; the sample outlet is connected to the inlet of the trap (4); the outlet of the trap (4) is switchably connected to the inlet of the gas detection unit (2) or to the inlet of the gas collection and metering device; the carrier gas outlet is switchably connected to or not connected to the inlet of the trap (4); The gas detection unit (2) comprises a non-polar chromatographic column (10), a microplate flow divider (15), a first detection channel and a second detection channel, wherein the first detection channel comprises a first damping column (12) and a mass spectrometer detector (14); the second detection channel comprises a second damping column (11) and a sulfur chemiluminescence detector (13); the inlet of the non-polar chromatographic column (10) is connected to the inlet of the gas detection unit (2), the outlet of the non-polar chromatographic column (10) is connected to the inlet of the microplate flow divider (15), the first outlet of the microplate flow divider (15) is connected to the inlet of the first detection channel, and the second outlet of the microplate flow divider (15) is connected to the inlet of the second detection channel.

2. The system according to claim 1, wherein: The temperature control device comprises a liquid nitrogen refrigerator (6) and a heater (7); The trap (4) is a stainless steel pipeline that has been inertized.

3. The system according to claim 1, wherein: The sample injector (3) is a six-way switching valve; The six-way switching valve comprises a first interface (31), a second interface (32), a third interface (33), a fourth interface (34), a fifth interface (35) and a sixth interface (36); The first interface (31) is in communication with the inlet of the gas collection and metering device, the second interface (32) is in communication with the outlet of the trap (4), the third interface (33) is in communication with the inlet of the gas detection unit (2), the fifth interface (35) is in communication with the inlet of the trap (4), the fourth interface (34) is formed as the carrier gas inlet, the fifth interface (35) is formed as the sample outlet or the carrier gas outlet, and the sixth interface (36) is formed as the sample inlet; The six-way switching valve has a closed state and an open state; In the closed state, the fourth interface (34) is in communication with the third interface (33), the fifth interface (35) is in communication with the sixth interface (36), so that the sample inlet is in communication with the inlet of the trap (4), and the first interface (31) is in communication with the second interface (32), so that the inlet of the gas collection and metering device is in communication with the outlet of the trap (4); In the open state, the fourth interface (34) is connected to the fifth interface (35) so that the carrier gas inlet is connected to the inlet of the trap (4), and the second interface (32) is connected to the third interface (33) so that the outlet of the trap (4) is connected to the inlet of the gas detection unit (2).

4. The system according to claim 3, wherein: The gas collection and metering device comprises a pump (8) and a metering tank (5); The gas inlet of the pump (8) is connected to the inlet of the metering tank (5) through the first pipeline (21) and the second pipeline (22), and the inlet of the metering tank (5) is connected to the first interface (31) through the second pipeline (22) and the third pipeline (20); The first pipeline (21) is provided with a first control valve, the second pipeline (22) is provided with a second control valve, and the third pipeline (20) is provided with a third control valve.

5. The system according to claim 1, wherein: The first damping column (12) and the second damping column (11) are each independently an elastic quartz chromatographic column; the first damping column (12) and the second damping column (11) have a column length of 1-2 m and an inner diameter of 0.1-0.18 mm; The stationary phase of the non-polar chromatographic column (10) is dimethyl polysiloxane, the column length is 70-105 m, and the inner diameter is 0.32-0.53 mm.

6. The system according to claim 3, wherein: The gas concentration unit (1) further comprises a sample transmission pipeline (16), and the gas detection unit (2) further comprises an inertization treatment two-way valve (9); The third interface (33) is connected to the inlet of the sample transmission pipeline (16), the outlet of the sample transmission pipeline (16) is connected to the inlet of the inert treatment two-way (9), and the outlet of the inert treatment two-way (9) is connected to the inlet of the non-polar chromatographic column (10).

7. The system according to claim 1, wherein: The detection limit of the system for sulfur-containing compounds is 0.01×10 - 9 mol / mol, the detection limit of formaldehyde is 1×10 -9 mol / mol, and the detection limit for formic acid is 0.1×10 -6 mol / mol.

8. A method for measuring the concentration of trace impurities in hydrogen using the system according to any one of claims 1 to 7, the method comprising: The temperature of the capture device is set at -180°C to -150°C, the preset volume of the hydrogen to be measured is introduced into the gas concentration unit (1), the hydrogen to be measured flows through the capture device to capture trace impurities in the hydrogen to be measured, and the preset volume of the hydrogen to be measured is introduced into the gas collection and metering device for metering; The temperature of the capture device is set at 60-100° C. to release the trace impurities and obtain a gas mixture; The gas mixture carried by the carrier gas is introduced into the gas detection unit (2) for detection.

9. The method according to claim 8, wherein: The step of introducing the gas mixture carried by the carrier gas into the gas detection unit (2) for detection comprises: Allowing the gas mixture carried by the carrier gas to flow through the non-polar chromatographic column (10) and the microplate flow divider (15) in sequence to obtain a first outflow component and a second outflow component; Allowing the first effluent component to enter the mass spectrometer detector (14) for a first detection; The second effluent component is allowed to enter the sulfur chemiluminescence detector (13) for second detection.

10. The method according to claim 9, wherein: The conditions of the first detection include: ion source temperature of 200-300° C., quadrupole temperature of 100-200° C., EI ion source voltage of 5-240 eV, and interface temperature of 200-400° C.; The conditions of the second detection include: a typical temperature of the burner is 800-850°C, a pressure of the dual plasma controller is 40-53.3 kPa, a flow rate of H2 is 40-50 mL / min, a flow rate of the oxidant gas is 50-55 mL / min, and a pressure of the ozone reaction cell is 0.67-1.33 kPa.

11. The method according to claim 8, wherein: The method includes: The temperature of the trap (4) is set to -180°C to -150°C, the six-way switching valve is in a closed state, the sample inlet is connected to the inlet of the trap (4), so that the hydrogen gas to be measured enters the trap (4), the trace impurities in the hydrogen gas to be measured are captured at low temperature, and the inlet of the gas collection and metering device is connected to the outlet of the trap (4), so that a preset volume of the hydrogen gas to be measured enters the gas collection and metering device for metering; The temperature of the trap (4) is set at 60-100° C. to release the trace impurities and obtain a gas mixture; The six-way switching valve is placed in an open state, the carrier gas inlet is connected to the inlet of the trap (4), and the outlet of the trap (4) is connected to the inlet of the gas detection unit (2), so that the carrier gas enters the trap (4) and carries the gas mixture into the gas detection unit (2) for detection.

12. The method according to claim 8, wherein: The content of sulfur compounds in the hydrogen to be tested is 0.01×10 -9 -10×10 -9 mol / mol, the formaldehyde content is 1×10 -9 -20×10 -9 mol / mol, the content of formic acid is 0.1×10 -6 -1×10 -6 mol / mol; the hydrogen to be tested is hydrogen for fuel cell vehicles.

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