Device and method for high-precision analysis of greenhouse gases N2O and SF6 in atmosphere

Abstract

The invention provides a device and a method for high-precision analysis of greenhouse gases N2O and SF6 in atmosphere, gas is fed through a gas path hole of a ten-port selector valve, a gas outlet of the ten-port selector valve is connected with a pressure flow controller PCMA of a gas chromatograph for gas discharge, and the PCMA is connected with a ten-way two-position switching valve; two ends of the quantitative loop are connected with a ten-way two-position switching valve; two ends of the chromatographic column pre-column are connected with a ten-way two-position switching valve; one end of the chromatographic column analysis column is connected with the ten-way double-position switching valve, and the other end of the chromatographic column analysis column is connected with the four-way double-position switching valve; and the four-way double-position switching valve is connected with the microelectronic capture detector. According to the technical scheme, two greenhouse gases such as N2O and SF6 in the atmosphere can be effectively and simultaneously analyzed at high precision, the accuracy of the analysis result is high, and the method is easy to implement.

Description

Technical Field

[0001] The embodiments of the present disclosure generally relate to the field of greenhouse gas observation and analysis, and more particularly, to an apparatus and method for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere based on gas chromatography. Background Art

[0002] Global warming caused by the greenhouse effect has become an environmental issue of global concern. N2O and SF6 are important greenhouse gases after CO2 and CH4. The warming effect of N2O on a 100-year scale is 298 times that of CO2, and its contribution to the global greenhouse effect is about 6%. SF6 is the most powerful greenhouse gas known to mankind, with a residence time in the atmosphere of 3,200 years and a warming effect 22,800 times that of CO2. With the development of my country's economy and the increasing attention paid to climate change, more and more institutions have begun to observe major greenhouse gases and related trace components. The variability of N2O and SF6 in the atmosphere is extremely low, so the analytical precision and accuracy of the analysis system are extremely high. The requirements given by the World Meteorological Organization / Atmospheric Observation Program are 0.3*10 -9 and 0.05*10 -12 (Volume percentage). Currently reported N2O and SF6 analyses primarily focus on trace impurities in specialized gases (e.g., standard gases) (e.g., N2O or SF6 in nitrogen), primarily using gas chromatography. However, these methods do not meet the precision requirements for analyzing atmospheric N2O and SF6. There are also reports using optical methods to analyze atmospheric N2O alone, but these methods are not capable of simultaneously analyzing atmospheric SF6.

[0003] In order to save costs, it is necessary to develop an analytical method that can simultaneously analyze N2O and SF6 in the atmosphere with an accuracy that meets the requirements of the World Meteorological Organization / Atmospheric Observation Program (WMO / GAW) (i.e., the analytical precision and accuracy of N2O and SF6 are within ±0.3*10 -9 and ±0.05*10 -12 within the scope). Summary of the Invention

[0004] In order to solve or at least partially solve the above-mentioned defects, according to an embodiment of the present disclosure, a device and method for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere are provided, which realizes the effective and simultaneous high-precision analysis of two greenhouse gases, such as N2O and SF6, in the atmosphere.

[0005] In a first aspect of the present disclosure, a device for high-precision analysis of atmospheric greenhouse gases N2O and SF6 is provided. The device comprises a gas chromatograph including a microelectron capture detector, a pressure flow controller (PCM), and a chromatographic column; wherein the pressure flow controller (PCM) comprises a PCMA, PCMB, PCMC, PCMD, and PCME; and the chromatographic column comprises a pre-column and an analytical column.

[0006] The temperature control valve box is equipped with a ten-port selection valve, a ten-way two-position switching valve, a four-way two-position switching valve, and a quantitative ring.

[0007] Air is taken in through one of the air passage holes of the ten-port selector valve, and the air outlet of the ten-port selector valve is connected to the pressure flow controller PCMA of the gas chromatograph for air discharge, and the PCMA is connected to the ten-way two-position switching valve;

[0008] The ten-port selector valve is also connected to seven standard gas cylinders, which respectively provide working standard gas, target standard gas, calibration standard gas 1, calibration standard gas 2, calibration standard gas 3, calibration standard gas 4, and calibration standard gas 5;

[0009] Both ends of the quantitative ring are connected to the ten-way two-position switching valve;

[0010] Both ends of the chromatographic column pre-column are connected to a ten-way two-position switching valve; one end of the chromatographic column analytical column is connected to a ten-way two-position switching valve, and the other end is connected to a four-way two-position switching valve;

[0011] The four-way two-position switching valve is connected to the microelectron capture detector.

[0012] According to the above aspects and any possible implementation, a further implementation is provided, wherein high-purity nitrogen carrier gas is connected to the PCMC, and the PCMC is connected to one gas path hole of the ten-way two-position switching valve.

[0013] According to the above aspects and any possible implementation, an implementation is further provided, wherein 5% methane argon (P5) carrier gas is connected to the PCMD, and the PCMD is connected to one gas path hole of the ten-way two-position switching valve.

[0014] According to the above aspects and any possible implementation, a further implementation is provided, in which a needle valve is connected to an air path hole of the ten-way two-position switching valve.

[0015] According to the aspects described above and any possible implementation method, an implementation method is further provided, in which a needle valve is provided to connect an air path hole of the four-way two-position switching valve, so as to discharge the first oxygen peak through the needle valve, thereby preventing the microelectron capture detector from being interfered with by oxygen impurities in the air.

[0016] According to the above aspects and any possible implementation, an implementation is further provided, wherein the ten-way two-position switching valve is connected to the PCMB to ensure the stability of the pressure at the outlet end of the quantitative loop and increase the quantitative volume of the quantitative loop.

[0017] According to the above aspects and any possible implementation, there is further provided an implementation, further comprising a pre-processing device for effectively removing particulate matter and water vapor from the air sample in the atmosphere;

[0018] The dew point alarm device is used to automatically cut off the gas path when the sample gas exceeds the humidity threshold to avoid damage to the subsequent chromatogram and detector due to water vapor; the dew point alarm device includes a dew point transmitter, a micro overflow valve, a three-way valve, and a three-way solenoid valve, wherein,

[0019] After the sample gas passes through the pretreatment device, it is connected to the tee through a pipeline. One end of the tee is connected to the dew point transmitter, and the other end is connected to the three-way solenoid valve. One end of the three-way solenoid valve is connected to the micro overflow valve and the other end is connected to the ten-port selection valve of the temperature control valve box.

[0020] In a second aspect of the present disclosure, a method for high-precision analysis of the greenhouse gases N2O and SF6 in the atmosphere is provided, which is based on the apparatus for analyzing the greenhouse gases N2O and SF6 in the atmosphere provided in the first aspect of the present disclosure. The method comprises:

[0021] Air is introduced through one of the gas path holes of the ten-port selector valve. In the injection state, the ten-way two-position switching valve controls the connection between the PCMA pipeline and the quantitative loop pipeline, controls the gas flow into the quantitative loop in the temperature-controlled valve box, and fully flushes and quantifies the quantitative tube;

[0022] After the flushing and quantification of the quantitative loop are completed, the ten-way two-position switching valve is switched, and the high-purity nitrogen carrier gas carries the sample gas or standard gas in the quantitative loop through the PCMC into the rear-end chromatographic column for separation, wherein the chromatographic column includes a pre-column and an analytical column; the sample gas or standard gas first passes through the pre-column and then passes through the analytical column, and then the gas separated in the order of peak elution flows to the four-way two-position switching valve;

[0023] After the oxygen peak passes through the chromatographic column but before entering the microelectron capture detector, switch the four-way double-position switching valve to discharge the oxygen through the needle valve;

[0024] Then, the four-way two-position switching valve is controlled to switch to the pipeline connected to the microelectron capture detector, so that N2O and SF6 enter the microelectron capture detector for qualitative and quantitative analysis.

[0025] According to the above aspects and any possible implementation, there is further provided an implementation, which further includes:

[0026] After passing through the pretreatment device, the sample gas enters the dew point alarm device. When the dew point transmitter detects that the water vapor content of the sample gas exceeds the set value, the control gas circuit is switched to the micro overflow valve port in the three-way solenoid valve, cutting off the gas connection between the sample gas and the ten-port selection valve; when it is detected that the water vapor content in the sample gas is less than the set value, the control three-way solenoid valve is switched back to the connection pipeline between the sample gas and the ten-port selection valve.

[0027] According to the above aspects and any possible implementation, there is further provided an implementation, further comprising:

[0028] The concentrations of the air sample and the target standard gas are calculated using a single-point linear and multi-point curve correction method, including: setting a gas analysis sequence, including sequence 1: working standard gas-air sample gas-working standard gas-target standard gas-working standard gas and sequence 2: calibration standard gas 1-calibration standard gas 2-working standard gas-calibration standard gas 3-calibration standard gas 4-calibration standard gas 5; and further, performing the following steps:

[0029] Step 1: Based on the data obtained from sequence 1, calculate the preliminary concentrations of N2O and SF6 according to formula (1).

[0030] C=Cw*(A1+A2) / (2*Aw) (1)

[0031] in:

[0032] C——Preliminary concentration of air sample (or target standard gas);

[0033] A1——The peak area (or peak height) of the working standard gas in front of the air sample (or target standard gas);

[0034] A2——The peak area (or peak height) of the working standard gas behind the air sample (or target standard gas);

[0035] Aw——peak area (or peak height) of working standard gas;

[0036] Cw——nominal value of working standard gas;

[0037] Step 2: Based on the data obtained from sequence 2, the nonlinear correction coefficient is fitted according to formula (2), and the coefficients a2, a1, and a0 of the quadratic equation are fitted using the least squares method.

[0038] y=a²x 2 +a1x+a0 (2)

[0039] y: Ratio of the peak area or peak height of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the working standard gas;

[0040] x: ratio of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the nominal value of the working standard gas;

[0041] Step 3: Based on the quadratic equation coefficients obtained in step 2, the initial concentration obtained in step 1 is corrected. The correction formula is as shown in formula (3):

[0042]

[0043] Where: C' - final concentration after correction

[0044] Step 4: Subtract the nominal value from the calculated value of the target standard gas to determine whether the observed result meets the requirements.

[0045] The present invention provides a gas analysis device based on gas chromatography analysis that can be used to analyze the concentration of N2O and SF6 in the atmosphere and a method for calculating their concentrations. In this process, a sample gas pretreatment device is first used to effectively remove particulate matter and water vapor in the air sample in the atmosphere to meet the chromatographic injection requirements, and a dew point alarm device is used to automatically cut off the sample gas path when the humidity threshold is exceeded, thereby avoiding damage to subsequent chromatographs and detectors due to water vapor; secondly, the process uses a pressure flow control module (PCM) to perform back pressure treatment on the quantitative loop, increase the quantitative volume in the quantitative loop, and at the same time control the injection flow with high precision of ±1%, reducing the use of mass flow meters to make the system structure more compact and save installation costs; then, the process designs the switching valve and the quantitative loop in a temperature-controlled valve box, and performs ±0.01°C precise temperature control on the temperature-controlled valve box, which can reduce the impact of temperature changes on the volume changes of the quantitative loop and valve switching on the pressure changes of the gas path. , improving the accuracy of gas chromatography analysis; in addition, the process effectively separates N2O and SF6 by using a combined chromatographic column and adopts valve control to cut off the oxygen peak, so that the microelectron capture detector is not interfered with by oxygen impurities in the air when accurately collecting signals, thereby effectively improving the sensitivity and measurement range of the instrument; finally, the process proposes a sequence of alternating operation of air sample, working standard gas, and target standard gas and a sequence of alternating operation of target standard gas and calibration standard gas by controlling the selector valve. Based on these two sequences, a concentration calculation method combining single point and multi-point is adopted, which enables the process to maintain a high sampling frequency (one observation value every 20 minutes) for analyzing atmospheric samples while achieving analysis accuracy control within the ±0.3*10 required by the World Meteorological Organization / Atmosphere Monitoring Program. -9 and ±0.05*10 -12 Within the scope of the data, making it internationally comparable can provide a basis for evaluating the effectiveness of the implementation of the national "carbon peak and carbon neutrality" policy.

[0046] Therefore, the present invention realizes the effective and simultaneous high-precision analysis of two greenhouse gases, namely N2O and SF6, in the atmosphere, and the analysis results are highly accurate and easy to implement.

[0047] It should be understood that the contents described in the Summary of the Invention section are not intended to limit the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, wherein:

[0049] Figure 1 A schematic structural diagram of a device for analyzing N2O and SF6 in the atmosphere provided by an embodiment of the present invention is shown;

[0050] Figure 2 The fitting equation obtained by fitting sequence 2 in the embodiment is shown.

[0051] in, Figure 1 The corresponding relationship between the reference numerals and component names is as follows:

[0052] 1. Pretreatment device; 2. Three-way valve; 3. Dew point transmitter; 4. Three-way solenoid valve; 5. Micro overflow valve; 6. Ten-port selection valve; 7. Ten-way two-position switching valve; 8. Four-way two-position switching valve; 9. Quantitative loop; 10. Needle valve; 11. Microelectron capture detector; 12. PCMA; 13. PCMB; 14. PCMC; 15. PCMD; 16. PCME; 17. Chromatographic column (pre-column); 18. Chromatographic column (analytical column); 19. Standard gas cylinder; 20. 5% methane argon (P5) carrier gas; 21. High-purity nitrogen carrier gas; 22. Temperature-controlled valve box. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0054] In this document, the term "and / or" simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0055] The present disclosure provides a device and method for high-precision analysis of the greenhouse gases N2O and SF6 in the atmosphere. The gas analysis device is constructed based on gas chromatography, and a method for calculating the concentrations of multiple greenhouse gases in the atmosphere is proposed based on the device, thereby achieving effective and simultaneous high-precision analysis of multiple greenhouse gases such as N2O and SF6.

[0056] Refer to the following Figure 1 The apparatus for analyzing greenhouse gases in the atmosphere with high precision provided by an embodiment of the present invention is described below. In this embodiment, the apparatus is used to analyze the concentrations of N2O and SF6 in the atmosphere.

[0057] like Figure 1 As shown, the device for analyzing greenhouse gases N2O and SF6 in the atmosphere provided according to an embodiment of the present invention includes a pretreatment device, a dew point alarm device, a gas chromatograph, a temperature-controlled valve box, carrier gas, calibration gas, a needle valve, a pressure reducing valve and several stainless steel pipelines.

[0058] Pretreatment device 1 is used to effectively remove particulate matter and water vapor from atmospheric air samples, meeting chromatographic sampling requirements. Existing equipment can be used. After the sample is filtered, dusted, dehydrated, and pressure-controlled by the pretreatment device, the particulate matter content is preferably controlled to 0.2 μm or less, the water vapor content is less than or equal to -30°C (0.0375%), and the sample pressure is maintained at 15 psi.

[0059] The dew point alarm automatically shuts off the gas line when the sample gas exceeds a humidity threshold, preventing moisture from damaging the subsequent chromatograph and detector. The dew point alarm includes two dew point transmitters (3), two micro-relief valves (5), two 1 / 4-way three-way valves (2), and two 1 / 4-way three-way solenoid valves (4).

[0060] After passing through the pretreatment device 1, the sample gas is connected to the tee 2 through a stainless steel pipe. One end of the tee 2 is connected to the dew point transmitter 3, and the other end is connected to the three-way solenoid valve 4. One end of the three-way solenoid valve 4 is connected to the micro-relief valve 5 and the other end is connected to the ten-port selection valve 6 of the temperature control valve box 22. Air is introduced through one air path hole of the ten-port selection valve 6. In this embodiment, two gas sampling ports are provided, which can collect gas at different heights according to actual needs, forming two sampling air paths connected to the pretreatment device 1. The two tees 2, two dew point transmitters 3, two three-way solenoid valves 4, and two micro-relief valves 5 after the pretreatment device 1 are arranged in parallel to form two air paths. The purpose of dew point monitoring through the dew point alarm device is to monitor whether the water vapor content in the sample gas is greater than or equal to the set value. In this embodiment, the set value is -30°C (0.0375%). When the dew point transmitter detects that the water vapor content of the sample gas is greater than or equal to -30℃ (0.0375%), the control gas circuit automatically switches to the port of the micro overflow valve 5 in the three-way solenoid valve 4, cutting off the gas connection between the sample gas and the chromatograph; when the water vapor content in the sample gas is detected to be less than -30℃ (0.0375%), the control three-way solenoid valve 4 automatically switches back to the connecting pipeline between the sample gas and the chromatograph.

[0061] In this embodiment, preferably, the accuracy of the dew point transmitter 3 is ±2°C; the micro overflow valve 5 allows the medium to be air, with a working pressure range of 0-130psi and a working temperature range of 0-60°C; the 1 / 4 three-way valve 2 is made of 316L stainless steel; the valve material of the 1 / 4 three-way solenoid valve 4 is 316L stainless steel, with an IP65 protection grade.

[0062] The temperature-controlled valve box 22 includes a ten-port selector valve 6, a ten-port two-position switching valve 7, a four-port two-position switching valve 8, and a quantitative loop 9. The gas chromatograph includes a microelectron capture detector 11, five pressure flow controllers (PCMs) (PCMA 12, PCMB 13, PCMC 14, PCMD 15, and PCME 16), and two chromatographic columns (a precolumn 17 and an analytical column 18).

[0063] The gas outlet of the ten-port selection valve 6 of the temperature control valve box 22 is connected to the pressure flow controller PCMA12 of the gas chromatograph, and the PCMA12 is connected to the ten-way two-position switching valve 7.

[0064] The ten-port selection valve 6 is also connected to seven standard gas cylinders 19. Preferably, each of the seven standard gas cylinders 19 is equipped with a two-stage pressure reducing valve. The standard gas is connected to the ten-port selection valve 6 after the pressure is adjusted by the high-precision two-stage pressure reducing valve. The pressure after the valve is 15Psi. The automatic switching between the sample gas and the standard gas can be achieved through the ten-port selection valve 6. The seven standard gas cylinders 19 respectively provide working standard gas (W), target standard gas (TG), calibration standard gas 1 (P1), calibration standard gas 2 (P2), calibration standard gas 3 (P3), calibration standard gas 4 (P4), and calibration standard gas 5 (P5). All standard gases are ambient air with clean air as the base gas, and the container is a 29.5L internally electropolished aluminum alloy high-pressure steel cylinder. The standard gas concentration value can be traced back to the first-level standard maintained by the World Meteorological Organization / Atmosphere Monitoring Program (WMO / GAW).

[0065] The two ends of the quantitative loop 9 are connected to the ten-way two-position switching valve 7. In the injection state, the ten-way two-position switching valve 7 controls the connection between the PCMA12 pipeline and the quantitative loop 9 pipeline, controls the gas flow into the quantitative loop 9 in the temperature control valve box 22, and fully flushes and quantifies the quantitative tube. The purpose of flushing is to remove the residual sample gas or standard gas from the last time and reduce the measurement error caused by the memory effect.

[0066] One air path hole of the ten-way two-position switching valve 7 is connected to PCMB13. One end of PCMB13 is connected to the ten-way two-position switching valve 7, and the other end is connected to the air. PCMB13 is set to a specified pressure to ensure the stability of the pressure at the air outlet end of the quantitative ring 9 and increase the quantitative volume of the quantitative ring 9.

[0067] The two ends of the chromatographic pre-column 17 are connected to a ten-way two-position switching valve 7. One end of the chromatographic analytical column 18 is connected to the ten-way two-position switching valve 7, and the other end is connected to a four-way two-position switching valve 8. High-purity nitrogen carrier gas 21 is connected to the PCMC 14, which is connected to one gas path port of the ten-way two-position switching valve 7. 5% methane argon (P5) carrier gas 20 is connected to the PCMD 15, which is connected to one gas path port of the ten-way two-position switching valve 7. A needle valve 10 is connected to one gas path port of the ten-way two-position switching valve 7. Another needle valve 10 is also provided to connect to one gas path port of the four-way two-position switching valve 8. 5% methane argon (P5) carrier gas 20 is also connected to the PCME 16, which is connected to one gas path port of the four-way two-position switching valve 8. The four-way two-position switching valve 8 is connected to the microelectron capture detector 11.

[0068] Through the above-mentioned structural arrangement, the ten-way two-position switching valve 7 is switched after the flushing and quantification of the quantitative loop 9 are completed. The high-purity nitrogen carrier gas 21 brings the sample gas or standard gas in the quantitative loop 9 into the two chromatographic columns (pre-column 17 and analytical column 18) at the rear end through PCMC14 for separation. In this embodiment, the existing pre-column and main column analytical column can be used according to actual analysis needs. The pre-column 17 is used to saturate the mobile phase and filter impurities to improve the accuracy of the analysis; the analytical column 18 is used for the effective separation and purification of the mixed gas. The sample gas or standard gas first passes through the pre-column 17 and then passes through the analytical column 18, and then the gas separated in the order of peaks flows to the four-way two-position switching valve 8. According to the peak order of the chromatographic columns, the oxygen peak emerges first. After the oxygen passes through analytical column 18 but before entering microelectron capture detector 11, four-way dual-position switching valve 8 is controlled to switch to discharge the oxygen through needle valve 10. Simultaneously, 5% methane argon (P5) carrier gas 20 is connected to microelectron capture detector 11 through PCME 16, ensuring that carrier gas continues to enter microelectron capture detector 11 during the oxygen discharge process, thus protecting the detector. After the oxygen is vented, four-way dual-position switching valve 8 is controlled to switch back to the pipeline connected to microelectron capture detector 11, allowing N2O and SF6 to enter microelectron capture detector 11 for qualitative and quantitative analysis.

[0069] After SF6 passes through pre-column 17, a ten-way, two-position switching valve 7 is controlled to switch. High-purity nitrogen carrier gas 21, precisely controlled by PCMC 14, backflushes pre-column 17 and is then exhausted through needle valve 10, connected to the ten-way, two-position switching valve 7. This backflushes away components with long retention times, such as CO2 and H2O, reducing column contamination and shortening analysis time. Argon (P5) carrier gas 20, containing 5% methane, is then connected to the main analytical column 18 via a ten-way, two-position switching valve at a flow rate of 30 ml / min via PCMD 15. This ensures a continuous carrier gas supply during the backflushing process, ensuring that N2O and SF6 can enter the detector for analysis.

[0070] The system analysis process, run sequence control, and data acquisition are controlled and processed by the chromatography workstation software. Through the combined operation of these multiple hardware components, the parameters of the voltage signal peaks generated by N₂O and SF₂ on the microelectron capture detector 11 were ultimately obtained, including retention time, peak height, peak area, peak width, and peak shape.

[0071] In this embodiment, preferably, in the temperature-controlled valve box 22, the ten-port selection valve 6 is set to a valve head aperture of 0.75mm, an operating temperature range of 0-200°C, and a working pressure of 0-400psi; the ten-way two-position switching valve 7 is set to a valve head aperture of 0.75mm, an operating temperature range of 0-225°C, and a working pressure of 0-400psi; the four-way two-position switching valve 8 is set to a valve head aperture of 0.75mm, an operating temperature range of 0-225°C, and a working pressure of 0-400psi; the quantitative ring 9 is made of 316L stainless steel and has a capacity volume of 5ml; the temperature control accuracy of the temperature-controlled valve box 22 is ±0.01°C.

[0072] In this embodiment, preferably, in the gas chromatograph, the microelectron capture detector 11 has a minimum detection limit of less than 0.006 pg / sec (benzene hexachloride) and a maximum operating temperature of 400°C; the pressure flow controller (PCM) PCMA12 accurately controls the inlet flow rate with a flow control accuracy of ±0.01 ml / min; the pressure flow controller (PCM) PCMB13 accurately adjusts the back pressure to ensure the stability of the outlet pressure with a pressure control accuracy of ±0.01 psi; the pressure flow controller (PCM) PCMC14 accurately controls the carrier gas / backflush gas flow rate with a flow control accuracy of ±0.01 ml / min; the pressure flow controller (PCM) PCMD15 accurately controls the auxiliary gas flow rate with a flow control accuracy of ±0.01 ml / min; the pressure flow controller (PCM) PCME16 accurately controls the auxiliary gas flow rate with a flow control accuracy of ±0.01 ml / min; the filling material of the chromatographic column pre-column 17 is Hayesep D 80-100 mesh, 2 meters in length, 1 / 8 inch in outer diameter, 2 mm in inner diameter; the filling material of the chromatographic column 18 is Hayesep D 80-100 mesh, 2 meters in length, 1 / 8 inch in outer diameter, and 2 mm in inner diameter; the dimensions of the gas chromatograph are 51 cm in length, 58 cm in width, and 49 cm in height, and the retention time reproducibility is <0.008%.

[0073] In this embodiment, preferably, the needle valve 10 is made of 316L stainless steel.

[0074] In this embodiment, preferably, the standard gas bottle 19 is made of aluminum, has a bottle volume of 29.5 L, and the inside of the bottle is processed using an electrolytic polishing process.

[0075] In this embodiment, preferably, the 5% methane argon (P5) carrier gas 20 is 95% argon (99.999%) with 5% methane added as the carrier gas; the high-purity nitrogen carrier gas 21 has a purity of 99.999%.

[0076] The gas analysis sequence was set up using the chromatography software, including Sequence 1 (working standard gas - air sample - working standard gas - target standard gas - working standard gas) and Sequence 2 (calibration standard gas 1 - calibration standard gas 2 - working standard gas - calibration standard gas 3 - calibration standard gas 4 - calibration standard gas 5). Sequence 1 was repeated for several consecutive runs, followed by a single run of Sequence 2, and then Sequence 1 was resumed. Furthermore, setting a target standard gas allowed for testing the long-term stability of the instrument. The concentrations of the air sample and target standard gas were calculated using single-point linear and multi-point curve calibration methods.

[0077] In this embodiment, the method of using single-point linear and multi-point curve calibration is described in detail as follows:

[0078] Step 1: Based on the data obtained in sequence 1, calculate the preliminary concentrations of N2O and SF6 according to formula (1).

[0079] C=Cw*(A1+A2) / (2*Aw) (1)

[0080] in:

[0081] C——Preliminary concentration of air sample (or target standard gas);

[0082] A1——The peak area (or peak height) of the working standard gas in front of the air sample (or target standard gas);

[0083] A2——The peak area (or peak height) of the working standard gas behind the air sample (or target standard gas);

[0084] Aw——peak area (or peak height) of working standard gas;

[0085] Cw——nominal value of working standard gas.

[0086] Step 2: Based on the data obtained from sequence 2, the nonlinear correction coefficient is fitted according to formula (2), and the coefficients a2, a1, and a0 of the quadratic equation are fitted using the least squares method.

[0087] y=a²x 2 +a1x+a0 (2)

[0088] y: Ratio of the peak area or peak height of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the working standard gas;

[0089] x: ratio of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the nominal value of the working standard gas;

[0090] Step 3: Based on the quadratic equation coefficients obtained in step 2, the initial concentration obtained in step 1 is corrected. The correction formula is as shown in formula (3).

[0091]

[0092] Where: C' - final concentration after correction

[0093] Step 4: Subtract the nominal value from the calculated value of the target standard gas to determine whether the observed result meets the WMO / GAW requirement of N2O±0.3*10 -9 and SF6±0.05*10 -12 .

[0094] Therefore, in the present invention, the concentration calculation method includes a sequence of single-point and multi-point alternating operations and a corresponding concentration calculation method. It not only has a single-point calculation analysis of sequence 1 that is continuously and reciprocally run for a long time, but also combines sequence 2 with a set time interval to perform analysis and calculation to form a multi-point monitoring. This sequence can ensure real-time early warning of the stability of the long-term operation of the analysis method and can effectively ensure that the analysis accuracy of the analysis method is maintained at ±0.3*10 -9 (N2O) and ±0.05*10 -12 (SF6) range.

[0095] According to the above-described device configuration and analysis method, in one embodiment, the following operating process is employed: an 80-meter tower is erected outdoors, and air is collected from 80 meters and 10 meters, respectively. The air collected from 80 meters is defined as upper-layer air, and the air collected from 10 meters is defined as lower-layer air. The collected air is filtered, dehydrated, and pressure-controlled by pretreatment device 1 to meet the requirements of particulate matter ≤ 0.2 μm, water vapor content ≤ 0.00388%, and pressure precisely controlled at 15 psi. It is then connected to the dew point transmitter 3 via the 1 / 4 tee 2. The dew point transmitter 3 sets the threshold value to -30°C (0.0375%) and performs interlocking control with the three-way solenoid valve 4 and the micro-relief valve 5 at the rear. When the dew point transmitter 3 detects that the water vapor content of the air is ≥-30°C (0.0375%), the three-way solenoid valve 4 is controlled to switch the pipeline to discharge the air above the water vapor threshold through the micro-relief valve 5; when the dew point transmitter 3 detects that the water vapor content of the air is <-30°C (0.0375%), the three-way solenoid valve 4 is controlled to switch back to the pipeline connected to the ten-port selection valve 6 at the rear end.

[0096] The ten-port selector valve 6 is also connected to seven standard gas cylinders 19 (each equipped with a two-stage pressure reducing valve, with a valve outlet pressure of 15Psi), which can realize automatic switching between sample gas and standard gas.

[0097] The outlet of the ten-port selector valve 6 is connected to PCMA 12, which is set to a flow rate of 30 ml / min and connected to the ten-port two-position switching valve 7. During the injection phase, the PCMA 12 tubing is connected to the tubing of the dosing loop 9, which is then flushed for 1.7 minutes to remove residual sample or calibration gas and reduce measurement errors. Simultaneously, PCMB 13 is set to a pressure of 10 psi to maintain a stable pressure at the outlet of the dosing loop 9 and increase the dosing volume.

[0098] After the flushing of the quantitative loop 9 is completed, the chromatographic software controls the ten-way two-position switching valve 7 to switch, and the high-purity nitrogen carrier gas 21 is set to a flow rate of 40 ml / min through PCMC14 to bring the sample gas or standard gas in the quantitative loop 9 into the pre-column 17 and the analytical column 18 for separation. According to the peak elution order of the chromatographic column, the oxygen peak is emitted first. After the oxygen passes through the chromatographic column but before entering the microelectron capture detector 11, the chromatographic software controls the four-way two-position switching valve 8 to switch, and the oxygen is discharged after passing through the needle valve 10. At the same time, the 5% methane argon (P5) carrier gas 20 is set to a flow rate of 25 ml / min through PCME16 and is connected to the microelectron capture detector 11, ensuring that carrier gas always enters the microelectron capture detector 11 during the oxygen discharge process, thereby protecting the detector.

[0099] The chromatographic software then controls the four-way, two-position switching valve 8 to switch again, switching back to the pipeline connected to the microelectron capture detector 11. N2O and SF6 enter the microelectron capture detector 11 for qualitative and quantitative analysis. After SF6 passes through the precolumn 17, the chromatographic software controls the ten-way, two-position switching valve 7 to switch. High-purity nitrogen carrier gas 21, with its flow precisely controlled by PCMC 14, backflushes the precolumn 17 and is exhausted through needle valve 10. 5% methane argon (P5) carrier gas 20, set at a flow rate of 30 ml / min by PCMD 15, connects to the analytical column 18 through the ten-way, two-position switching valve 7. This ensures that during the backflush of the precolumn 17, carrier gas is supplied to the downstream pipeline, ensuring that N2O and SF6 can enter the detector for analysis. The system analysis process, run sequence control, and data acquisition are controlled and processed by the chromatographic workstation software. This process ultimately obtains the response signal (peak area and peak height) of the microelectron capture detector 11.

[0100] The following uses single-point linear and multi-point curve calibration methods to calculate the concentrations of the air sample and target standard gas. Alphanumeric symbols are used to represent the following: Working Standard Gas (W), Upper Air (AH), Lower Air (AL), Target Standard Gas (TG), Calibration Standard Gas 1 (P1), Calibration Standard Gas 2 (P2), Calibration Standard Gas 3 (P3), Calibration Standard Gas 4 (P4), and Calibration Standard Gas 5 (P5). For N₂O analysis, Sequence 1 is set to WW-AH-W-AL-W-AH-W-AL-W-AH-W-TG-W, with this sequence running in a reciprocating pattern. The calculation results for the valve port number, peak area, nominal concentration of the working standard gas (target standard gas), and single-point concentration for a single run are shown in Table 1. Sequence 2 is set to W-P1-P2-P3-P4-P5-P1-P2-W-P3-P4-P5-P1-P2-W-P3-P4-P5-P1-P2-W, and this sequence is run once a month (or other adjustable interval). Based on the analysis of N2O in Sequences 1 and 2, calculations are performed according to the aforementioned single-point linear and multi-point curve calibration methods. The calculation results for the valve port number, peak area, nominal concentration of each standard gas, the ratio of the calibration standard gas to the nominal concentration of the working standard gas, and the ratio of the calibration standard gas to the average peak area of ​​the preceding and following working standard gases for a single run are shown in Table 2.

[0101] Table 1 Results of running sequence 1 once

[0102]

[0103] Table 2 Results of running sequence 2 once

[0104]

[0105]

[0106]

[0107] The ratio of the nominal concentration of the calibration standard gas to the working standard gas in Table 2 is taken as y, and the average peak area of ​​the calibration standard gas and the working standard gas before and after is taken as x. The fitting result of the quadratic equation is as follows: Figure 2 As shown, the equation coefficients are determined to be a2 = 0.2602, a1 = 0.4438, and a0 = 0.2959. The single-point method calculation results shown in Table 1 are corrected based on the equation coefficients. The correction results are shown in Table 3. The corrected concentration is the final observed concentration.

[0108] Table 3 Correction results of N2O concentration

[0109]

[0110] The calculated concentration of target standard gas TG is 333.97825*10 -9 Subtract its nominal concentration 333.94*10-9 0.03*10 -9 , less than 0.3*10 -9 Therefore, it is judged that the calculation results meet the requirements of WMO / GAW.

[0111] Furthermore, the analysis and calculation process of SF6 is the same as the above-mentioned calculation process of N2O, which will not be repeated here.

[0112] According to the embodiments of the present disclosure, the following technical effects are achieved:

[0113] The present invention provides a gas analysis device based on gas chromatography analysis that can be used to analyze the concentration of N2O and SF6 in the atmosphere and a method for calculating their concentrations. In this process, a sample gas pretreatment device is first used to effectively remove particulate matter and water vapor in the air sample in the atmosphere to meet the chromatographic injection requirements, and a dew point alarm device is used to automatically cut off the sample gas path when the humidity threshold is exceeded, thereby avoiding damage to subsequent chromatographs and detectors due to water vapor; secondly, the process uses a pressure flow control module (PCM) to perform back pressure treatment on the quantitative loop, increase the quantitative volume in the quantitative loop, and at the same time control the injection flow with high precision of ±1%, reducing the use of mass flow meters to make the system structure more compact and save installation costs; then, the process designs the switching valve and the quantitative loop in a temperature-controlled valve box, and performs ±0.01°C precise temperature control on the temperature-controlled valve box, which can reduce the impact of temperature changes on the volume changes of the quantitative loop and valve switching on the pressure changes of the gas path. , improving the accuracy of gas chromatography analysis; in addition, the process effectively separates N2O and SF6 by using a combined chromatographic column and adopts valve control to cut off the oxygen peak, so that the microelectron capture detector is not interfered with by oxygen impurities in the air when accurately collecting signals, thereby effectively improving the sensitivity and measurement range of the instrument; finally, the process proposes a sequence of alternating operation of air sample, working standard gas, and target standard gas and a sequence of alternating operation of target standard gas and calibration standard gas by controlling the selector valve. Based on these two sequences, a concentration calculation method combining single point and multi-point is adopted, which enables the process to maintain a high sampling frequency (one observation value every 20 minutes) for analyzing atmospheric samples while achieving analysis accuracy control within the ±0.3*10 required by the World Meteorological Organization / Atmosphere Monitoring Program. -9 and ±0.05*10 -12 Within the scope of the data, making it internationally comparable can provide a basis for evaluating the effectiveness of the implementation of the national "carbon peak and carbon neutrality" policy.

[0114] Therefore, the present invention realizes the effective and simultaneous high-precision analysis of two greenhouse gases, namely N2O and SF6, in the atmosphere, and the analysis results are highly accurate and easy to implement.

[0115] In this specification, the terms "connect," "install," and "fix" should be understood broadly. For example, "connect" can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0116] Throughout this specification, terms such as "one embodiment" or "some embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0117] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere, characterized in that: include: A gas chromatograph comprising a microelectron capture detector, a pressure flow controller (PCM), and a chromatographic column; wherein the pressure flow controller (PCM) comprises PCMA, PCMB, PCMC, PCMD, and PCME; and the chromatographic column comprises a pre-column and an analytical column; The temperature control valve box is equipped with a ten-port selection valve, a ten-way two-position switching valve, a four-way two-position switching valve, and a quantitative ring. Air is taken in through one of the air passage holes of the ten-port selector valve, and the air outlet of the ten-port selector valve is connected to the pressure flow controller PCMA of the gas chromatograph for air discharge, and the PCMA is connected to the ten-way two-position switching valve; The ten-port selector valve is also connected to seven standard gas cylinders, which respectively provide working standard gas, target standard gas, calibration standard gas 1, calibration standard gas 2, calibration standard gas 3, calibration standard gas 4, and calibration standard gas 5; Both ends of the quantitative ring are connected to the ten-way two-position switching valve; Both ends of the chromatographic column pre-column are connected to a ten-way two-position switching valve; one end of the chromatographic column analytical column is connected to a ten-way two-position switching valve, and the other end is connected to a four-way two-position switching valve; The four-way two-position switching valve is connected to the microelectron capture detector.

2. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: High-purity nitrogen carrier gas is connected to the PCMC, and the PCMC is connected to one gas path hole of the ten-way two-position switching valve.

3. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: The carrier gas of 5% methane in argon (P5) is connected to the PCMD, and the PCMD is connected to one gas path hole of the ten-way two-position switching valve.

4. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: The needle valve is connected to an air path hole of the ten-way two-position switching valve.

5. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: A needle valve is also provided to connect an air path hole of the four-way two-position switching valve, so as to discharge the first oxygen peak through the needle valve, thereby preventing the microelectronic capture detector from being interfered with by oxygen impurities in the air.

6. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: The ten-way two-position switching valve is connected to the PCMB to ensure the stability of the pressure at the outlet end of the quantitative loop and increase the quantitative volume of the quantitative loop.

7. The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 1, characterized in that: A pre-treatment device is also provided to effectively remove particulate matter and water vapor from the air sample in the atmosphere; The dew point alarm device is used to automatically cut off the gas path when the sample gas exceeds the humidity threshold to avoid damage to the subsequent chromatogram and detector due to water vapor; the dew point alarm device includes a dew point transmitter, a micro overflow valve, a three-way valve, and a three-way solenoid valve, wherein, After the sample gas passes through the pretreatment device, it is connected to the tee through a pipeline. One end of the tee is connected to the dew point transmitter, and the other end is connected to the three-way solenoid valve. One end of the three-way solenoid valve is connected to the micro overflow valve and the other end is connected to the ten-port selection valve of the temperature control valve box.

8. A method for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere, characterized in that: The device for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere as described in claims 1 to 6 comprises the following steps: Air is introduced through one of the gas path holes of the ten-port selector valve. In the injection state, the ten-way two-position switching valve controls the connection between the PCMA pipeline and the quantitative loop pipeline, controls the gas flow into the quantitative loop in the temperature-controlled valve box, and fully flushes and quantifies the quantitative tube; After the flushing and quantification of the quantitative loop are completed, the ten-way two-position switching valve is switched, and the high-purity nitrogen carrier gas carries the sample gas or standard gas in the quantitative loop through the PCMC into the rear-end chromatographic column for separation, wherein the chromatographic column includes a pre-column and an analytical column; the sample gas or standard gas first passes through the pre-column and then passes through the analytical column, and then the gas separated in the order of peak elution flows to the four-way two-position switching valve; After the oxygen peak passes through the chromatographic column but before entering the microelectron capture detector, switch the four-way double-position switching valve to discharge the oxygen through the needle valve; Then, the four-way two-position switching valve is controlled to switch to the pipeline connected to the microelectron capture detector, so that N2O and SF6 enter the microelectron capture detector for qualitative and quantitative analysis.

9. The method for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 8, characterized in that: Before the ten-port selector valve starts to intake air, the method further includes: After passing through the pretreatment device, the sample gas enters the dew point alarm device. When the dew point transmitter detects that the water vapor content of the sample gas exceeds the set value, the control gas circuit is switched to the micro overflow valve port in the three-way solenoid valve, cutting off the gas connection between the sample gas and the ten-port selection valve; when it is detected that the water vapor content in the sample gas is less than the set value, the control three-way solenoid valve is switched back to the connection pipeline between the sample gas and the ten-port selection valve.

10. The method for high-precision analysis of greenhouse gases N2O and SF6 in the atmosphere according to claim 9, characterized in that: Also includes: The concentrations of the air sample and the target standard gas are calculated using a single-point linear and multi-point curve correction method, including: setting a gas analysis sequence, including sequence 1: working standard gas-air sample gas-working standard gas-target standard gas-working standard gas and sequence 2: calibration standard gas 1-calibration standard gas 2-working standard gas-calibration standard gas 3-calibration standard gas 4-calibration standard gas 5; and further, performing the following steps: Step 1: Based on the data obtained from sequence 1, calculate the preliminary concentrations of N2O and SF6 according to formula (1). C= Cw * (A1+A2) / (2* Aw) (1) in: C——Preliminary concentration of air sample (or target standard gas); A1——The peak area (or peak height) of the working standard gas in front of the air sample (or target standard gas); A2——The peak area (or peak height) of the working standard gas behind the air sample (or target standard gas); Aw——peak area (or peak height) of working standard gas; Cw——nominal value of working standard gas; Step 2: Based on the data obtained from sequence 2, the nonlinear correction coefficient is fitted according to formula (2), and the coefficients a2, a1, and a0 of the quadratic equation are fitted using the least squares method. y =a2x 2 +a1x+a0 (2) y: Ratio of the peak area or peak height of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the working standard gas; x: ratio of the calibration standard gas (1 / 2 / 3 / 4 / 5) to the nominal value of the working standard gas; Step 3: Based on the quadratic equation coefficients obtained in step 2, the initial concentration obtained in step 1 is corrected. The correction formula is as shown in formula (3): Where: C' - final concentration after correction Step 4: Subtract the nominal value from the calculated value of the target standard gas to determine whether the observed result meets the requirements.

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