Separation, conversion and enrichment device for trace methane and nitrous oxide isotope components

Abstract

The utility model discloses a trace methane and nitrous oxide isotope component separation, conversion and enrichment device, and belongs to the technical field of isotope analysis and test. Comprising a methane sample tube, a nitrous oxide sample tube, a helium bottle, a first Nafion trap, a VOC adsorption trap, a combustion tube, a four-way valve, an eight-way valve, a carbon dioxide removal assembly, a first enrichment cold trap, a second enrichment cold trap and a chromatographic column, the helium tank is communicated with the gas inlet ends of the methane sample tube and the nitrous oxide sample tube, the gas outlet end of the methane sample tube is communicated with the first Nafion trap and the VOC adsorption trap, the VOC adsorption trap is communicated with the carbon dioxide removal assembly through a four-way valve, the carbon dioxide removal assembly is communicated with a combustion tube, the combustion tube is communicated with the first enrichment cold trap through an eight-way valve, and the combustion tube is communicated with the second enrichment cold trap through an eight-way valve. The first enrichment cold trap is communicated with a second enrichment cold trap through an eight-way valve, and the second enrichment cold trap is communicated with the chromatographic column. According to the utility model, methane or nitrous oxide gas in the air can be separated, converted and enriched, so that methane or nitrous oxide in the air can be measured by instruments such as a mass spectrometer and the like.

Description

Technical Field

[0001] This utility model belongs to the field of isotope analysis and testing technology, and in particular relates to a device for separating, converting and enriching trace methane and nitrous oxide isotope components. Background Technology

[0002] In recent years, people have gradually realized the impact of human activities on climate change. Identifying the source-sink processes of greenhouse gases and understanding their abundance in the atmosphere are of great significance for controlling global greenhouse gas emissions. Therefore, accurately measuring the content and isotopic composition of greenhouse gases in the atmosphere is crucial. Among the many greenhouse gases, methane (CH4) is the second largest greenhouse gas globally, characterized by high warming potential and a short lifespan. According to data from the World Meteorological Organization in 2023, the global average methane content reached 1923±2 nmol / mol. Due to the very low concentrations of methane and nitrous oxide in the atmosphere, direct headspace sampling via gasbench is not possible, and mass spectrometry cannot directly analyze methane gas.

[0003] To address this, a device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes is proposed. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model proposes a device for separating, converting and enriching trace amounts of methane and nitrous oxide isotope components.

[0005] To achieve the above objectives, this utility model provides a device for the separation, conversion, and enrichment of trace methane and nitrous oxide isotope components, comprising: a methane sample tube, a nitrous oxide sample tube, a helium cylinder, a first Nafion trap, a VOC adsorption trap, a combustion tube, a four-way valve, an eight-way valve, a carbon dioxide removal component, a first enrichment cold trap, a second enrichment cold trap, and a chromatographic column.

[0006] The helium cylinder is connected to the inlet of the methane sample tube and the nitrous oxide sample tube. The outlet of the methane sample tube is connected in sequence to the first Nafion trap and the VOC adsorption trap. The VOC adsorption trap is connected to the carbon dioxide removal component through a four-way valve. The carbon dioxide removal component is connected to a combustion tube. The combustion tube is connected to the first enrichment cold trap through an eight-way valve. The first enrichment cold trap is connected to the second enrichment cold trap through an eight-way valve. The second enrichment cold trap is connected to the chromatographic column.

[0007] According to the present invention, a device for separating, converting and enriching trace methane and nitrous oxide isotope components is provided, wherein the helium cylinder is connected to the methane sample tube, the nitrous oxide sample tube and the eight-way valve respectively through a helium flow controller.

[0008] According to the present invention, a device for separating, converting and enriching trace methane and nitrous oxide isotope components is provided. The four-way valve has four outlets: a, b, c, and d. The a port is connected to the VOC adsorption trap, the b port is connected to the outside, the c port is connected to the outlet of the nitrous oxide, and the d port is connected to the carbon dioxide removal component.

[0009] In methane mode, ports a and d of the four-way valve are connected; in nitrous oxide mode, ports c and d of the four-way valve are connected.

[0010] According to the present invention, a device for separating, converting and enriching trace methane and nitrous oxide isotopes is provided. The eight-way valve has eight outlets: A, B, C, D, E, F, G, and H. The A outlet is connected to the combustion tube. The two ends of the first enrichment cold trap are connected to the B outlet and the E outlet, respectively. The end of the second enrichment cold trap away from the chromatographic column is connected to the D outlet. The F outlet is connected to the outside. The C, G, and H outlets are connected to a helium cylinder through a helium flow controller.

[0011] In loading mode, ports A and H of the eight-way valve are connected, ports G and F are connected, ports E and D are connected, and ports C and B are connected; in injection mode, ports A and B of the eight-way valve are connected, ports C and D are connected, ports E and F are connected, and ports G and H are connected.

[0012] According to the present invention, a device for separating, converting and enriching trace methane and nitrous oxide isotope components is provided. The carbon dioxide removal component includes a chemical trap and an adsorption cold trap. One end of the chemical trap is connected to port d of the four-way valve, and the other end is connected to the adsorption cold trap. The end of the adsorption cold trap away from the chemical trap is connected to the combustion tube.

[0013] The present invention provides a device for separating, converting and enriching trace methane and nitrous oxide isotope components, which further includes a second Nafion trap connected to the gas outlet of the chromatographic column.

[0014] The device for separating, converting and enriching trace methane and nitrous oxide isotopes according to this utility model also includes a nitrogen cylinder, which is connected to the first Nafion trap through a nitrogen flow controller for purging.

[0015] According to the present invention, a device for separating, converting, and enriching trace methane and nitrous oxide isotope components is provided. The adsorption cold trap is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 0.75 mm, and its interior is filled with nickel wire; the first enrichment cold trap is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 0.75 mm, and its interior is inserted with nickel wire; the second enrichment cold trap is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 0.75 mm, and its interior is inserted with a 0.32 mm quartz deactivated capillary.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] This invention provides a device for the separation, transformation, enrichment, and purification of trace methane carbon isotope components in air, as well as a device for the purification and enrichment of nitrous oxide. It employs a pre-concentration method to remove CO2, followed by online oxidization of methane (CH4) to CO2. After separation by a chromatographic column, the CO2 is introduced into a mass spectrometer, where the m / z ratios at 44, 45, and 46 are measured. The carbon isotopes (δ¹⁴ and δ¹⁶) in the methane (CH4) are then calculated. 13 C) Composition: For nitrous oxide, CO2 is removed, and N2O is separated from a large amount of N2 and O2 through a special cold trap system. The N2O is transferred to a small-volume cold trap, released online, and then separated as blank CO2 by a chromatographic column. After Kr interference is removed by a Naflon trap, it enters a universal interface for measurement. This invention can separate, convert, and enrich methane or nitrous oxide gases in the air, allowing them to be measured by instruments such as mass spectrometers. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 This is a schematic diagram of the structure of the device for separating, converting and enriching trace methane and nitrous oxide isotopes according to this invention.

[0020] In the diagram: 1. Methane sample tube; 2. Nitrous oxide sample tube; 3. Helium cylinder; 4. First Nafion trap; 5. VOC adsorption trap; 6. Combustion tube; 7. Four-way valve; 8. Eight-way valve; 9. First enrichment cold trap; 10. Second enrichment cold trap; 11. Chromatographic column; 12. Helium flow controller; 13. Chemical trap; 14. Adsorption cold trap; 15. Second Nafion trap; 16. Nitrogen cylinder; 17. Nitrogen flow controller. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Partial Glossary:

[0023] Nafion traps: Nafion is a perfluorosulfonic acid polymer with a unique chemical structure and properties. The dehumidification principle of Nafion traps is based on their highly selective semi-permeable properties for water vapor. The driving force for dehumidification is the water vapor pressure gradient inside and outside the tube, i.e., the humidity difference, rather than the pressure difference or temperature difference.

[0024] VOC Adsorption Trap: A VOC (volatile organic compound) adsorption trap is a device used to capture and enrich volatile organic compounds. Its working principle is mainly based on the adsorption of VOCs by the adsorbent material. The adsorbent material typically has a highly porous structure, and these pores provide a large surface area. When a gas containing VOCs passes through the adsorption trap, the VOC molecules undergo physical or chemical adsorption on the surface of the adsorbent material.

[0025] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Reference Figure 1 As shown in this embodiment, when testing the carbon stable isotopes of methane (CH4), CH4 needs to be oxidized into CO2 gas that can be detected by mass spectrometry. Therefore, CO2 and trace amounts of carbon-containing organic matter in the sample gas must be removed before testing the sample.

[0027] First, the eight-way valve 8 switches to injection mode, and the first enrichment cold trap 9 falls into liquid nitrogen. The sample gas in the methane sample tube 1 is purged by the helium carrier gas input from the helium cylinder 3 through the helium flow controller 12 and enters the first Nafion trap 4 for dehydration. Then, it passes through the VOC adsorption trap 5 to remove large molecular organic matter in the gas sample. After that, it enters port a of the four-way valve 7, which is in methane mode. The sample gas enters from port a and exits from port d of the four-way valve 7. Then, it enters the chemical trap 13 to be absorbed and remove most of the CO2. Then, it enters the adsorption cold trap 14 to further remove the residual CO2. Then, it enters the combustion tube 6, which is set to 900°C. The CH4 in the sample gas is oxidized to CO2 in the 900°C combustion tube 6 and then enters the eight-way valve 8, which is now in injection mode. In the inlet mode, the gas passes through ports A and B of the eight-way valve 8 and is enriched in the first enrichment cold trap 9. As the enrichment in the first enrichment cold trap 9 is completed, the second enrichment cold trap 10 falls into the liquid nitrogen. The eight-way valve 8 switches to the loading mode, and the first enrichment cold trap 9 rises from the liquid nitrogen. The CO2 in the first enrichment cold trap 9 is vaporized and carried by the helium gas entering through port C into the second enrichment cold trap 10 for further enrichment. The volume of the second enrichment cold trap 10 is smaller than that of the first enrichment cold trap 9. After the enrichment in the second enrichment cold trap 10 is completed, the eight-way valve 8 switches to the injection mode, and the second enrichment cold trap 10 rises from the liquid nitrogen. The CO2 is vaporized and carried by the helium gas into the chromatographic column 11, separating CO2 and N2. The separated CO2 passes through the second Nafion trap 15 for further water removal and finally enters the stable isotope mass spectrometer for detection.

[0028] When testing the nitrogen stable isotopes of nitrous oxide (N₂O), the eight-way valve 8 is first switched to injection mode, and the first enrichment cold trap 9 falls into liquid nitrogen. The sample gas from the nitrous oxide sample tube 2, via the helium carrier gas input through the helium flow controller 12, purges the helium from the helium cylinder 3 into the four-way valve 7. At this time, the four-way valve 7 is in nitrous oxide mode. The sample gas enters the chemical trap 13 through ports C and D, where most of the CO₂ is removed. It then enters the adsorption cold trap 14 to remove the remaining CO₂, and then enters port A of the eight-way valve 8 through the combustion tube 6. The temperature of the combustion tube 6 is set below 90°C; in this embodiment, it is room temperature. The eight-way valve 8 is in injection mode at this time, and the sample gas is enriched through ports A and B of the eight-way valve 8. The first enrichment cold trap 9 is used for enrichment. As the enrichment in the first enrichment cold trap 9 is completed, the second enrichment cold trap 10 falls into the liquid nitrogen. The eight-way valve 8 switches to the loading mode, and the first enrichment cold trap 9 rises from the liquid nitrogen. The N2O in the first enrichment cold trap 9 is vaporized and carried by the helium gas entering through port C into the second enrichment cold trap 10 for further enrichment. The volume of the second enrichment cold trap 10 is smaller than that of the first enrichment cold trap 9. After the enrichment in the second enrichment cold trap 10 is completed, the eight-way valve 8 switches to the injection mode, and the second enrichment cold trap 10 rises from the liquid nitrogen. The N2O vaporization is carried by the helium gas into the chromatographic column 11, causing N2O and N2 to separate. The separated N2O passes through the second Nafion trap 15 for further water removal and finally enters the stable isotope mass spectrometry for detection.

[0029] The following are the results (Table 1) of a method for separating, converting, and enriching trace methane and nitrous oxide gas isotopes using a Delta VAdvantage stable isotope mass spectrometer (Thermo Fisher Scientific) coupled with an air sample to determine the carbon stable isotopes of methane and the nitrogen stable isotopes of nitrous oxide. The determinations showed excellent reproducibility, with standard deviations all less than 0.3‰.

[0030] Table 1. Results of stable carbon isotopes of methane and stable nitrogen isotopes of nitrous oxide in air samples.

[0031]

[0032] Any aspects of this utility model that are not detailed herein are conventional technical means known to those skilled in the art.

[0033] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0034] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes, characterized in that, include: Methane sample tube (1), nitrous oxide sample tube (2), helium bottle (3), first Nafion trap (4), VOC adsorption trap (5), combustion tube (6), four-way valve (7), eight-way valve (8), carbon dioxide removal assembly, first enrichment cold trap (9), second enrichment cold trap (10) and chromatographic column (11); The helium cylinder (3) is connected to the inlet of the methane sample tube (1) and the nitrous oxide sample tube (2). The outlet of the methane sample tube (1) is connected in sequence to the first Nafion trap (4) and the VOC adsorption trap (5). The VOC adsorption trap (5) is connected to the carbon dioxide removal assembly through a four-way valve (7). The carbon dioxide removal assembly is connected to a combustion tube (6). The combustion tube (6) is connected to the first enrichment cold trap (9) through an eight-way valve (8). The first enrichment cold trap (9) is connected to the second enrichment cold trap (10) through an eight-way valve (8). The second enrichment cold trap (10) is connected to the chromatographic column (11).

2. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 1, characterized in that: The helium cylinder (3) is connected to the methane sample tube (1), the nitrous oxide sample tube (2), and the eight-way valve (8) respectively through the helium flow controller (12).

3. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 1, characterized in that: The four-way valve (7) has four outlets: a, b, c, and d. The a port is connected to the VOC adsorption trap (5), the b port is connected to the outside, the c port is connected to the outlet of the nitrous oxide, and the d port is connected to the carbon dioxide removal component. In methane mode, ports a and d of the four-way valve (7) are connected; in nitrous oxide mode, ports c and d of the four-way valve (7) are connected.

4. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 1, characterized in that: The eight-way valve (8) has eight outlets: A, B, C, D, E, F, G, and H. The A outlet is connected to the combustion tube (6). The two ends of the first enrichment cold trap (9) are connected to the B outlet and the E outlet, respectively. The end of the second enrichment cold trap (10) away from the chromatographic column (11) is connected to the D outlet. The F outlet is connected to the outside. The C, G, and H outlets are connected to the helium cylinder (3) through the helium flow controller (12), respectively. In loading mode, ports A and H of the eight-way valve (8) are connected, ports G and F are connected, ports E and D are connected, and ports C and B are connected; in injection mode, ports A and B of the eight-way valve (8) are connected, ports C and D are connected, ports E and F are connected, and ports G and H are connected.

5. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 3, characterized in that: The carbon dioxide removal assembly includes a chemical trap (13) and an adsorption cold trap (14). One end of the chemical trap (13) is connected to port d of the four-way valve (7), and the other end is connected to the adsorption cold trap (14). The end of the adsorption cold trap (14) away from the chemical trap (13) is connected to the combustion tube (6).

6. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 1, characterized in that: It also includes a second Nafion trap (15), which is connected to the outlet end of the chromatographic column (11).

7. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 1, characterized in that: It also includes a nitrogen cylinder (16), which is connected to the first Nafion trap (4) via a nitrogen flow controller (17) for purging.

8. The device for separating, converting, and enriching trace amounts of methane and nitrous oxide isotopes according to claim 5, characterized in that: The adsorption cold trap (14) is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 1.0 mm, and is filled with nickel wire; the first enrichment cold trap (9) is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 0.75 mm, and is filled with nickel wire; the second enrichment cold trap (10) is a stainless steel tube with an outer diameter of 1 / 16 inch and an inner diameter of 0.75 mm, and is filled with a 0.32 mm quartz deactivating capillary.

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