CN111679025A - Gas chromatography detection system and method for determination of perfluoroisobutyronitrile gas composition - Google Patents

Abstract

The invention provides a gas chromatography detection system and method for measuring perfluoroisobutyronitrile gas components, comprising: a first analysis unit and a second analysis unit; the first analysis unit includes a first switching valve, a second There are three chromatographic columns, a third switching valve and a first detector; the first interface on the first switching valve is connected with the gas sample source to be tested; the third switching valve is provided with a second vent valve. The second analysis unit includes a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector connected in sequence; the first interface on the second switching valve is connected to the gas sample source to be measured; The second switching valve is provided with a third venting valve; the fourth switching valve is provided with a fourth venting valve. The gas chromatography system provided by the invention can realize the accurate analysis of all the components of the C ₄ F ₇ N-CO ₂ mixed gas decomposition products with only one instrument, which is beneficial to accurately judge the operation status of the electrical equipment; , reducing the analysis time.

Description

Gas chromatography detection system and method for determination of perfluoroisobutyronitrile gas composition

technical field

The invention relates to the technical field of analytical chemistry, in particular to a gas chromatography detection system and method for measuring perfluoroisobutyronitrile gas components.

Background technique

Gas-insulated electrical equipment usually uses sulfur hexafluoride (SF ₆ ) gas as the insulating medium, but due to the strong greenhouse effect of SF ₆ , its GWP value is about 23,900 times that of CO ₂ , which hinders the power grid in China and even the world. ECO development. Therefore, it has become a hot research topic at home and abroad in recent years to find SF ₆ substitute gas with comparable electrical properties and environmental friendliness. In 2014, French Alstom (ALSTOM) screened a gas perfluoroisobutyronitrile (C ₄ F ₇ N) named Novec™ 4710 from the refrigerant catalog of 3M Company in the United States. The insulation performance of C ₄ F ₇ N is more than 2.2 times that of SF ₆ under the same conditions, and the GWP (Global Warming Potential) is much lower than that of SF ₆ gas. But also suffering from higher liquefaction temperatures, ALSTOM had to mix Novec™ 4710 with CO ₂ . But because the liquefaction temperature is higher, it is usually mixed with CO ₂ , and the insulating strength of the mixed gas can still reach 87%~96% of SF ₆ under the same conditions. Because of its excellent performance, it has become a good substitute gas, and American General Company has applied it to 145kV GIS.

During the operation of electrical equipment, if the equipment fails, partial discharge and other phenomena may occur. Under discharge conditions, the C ₄ F ₇ N-CO ₂ mixed gas will decompose and may generate a large number of CF ₃ radicals, CN radicals, and CF radicals. The combination of these radicals will cause complex chemical reactions, such as CF ₃ . CN and other decomposition products, by detecting the content of these impurities, the operation status of the equipment can be inferred. At present, there is no systematic detection method for C ₄ F ₇ N-CO ₂ mixed gas on the market. Generally, multiple instruments are used for detection, such as TCD (thermal conductivity detector), FTIR, etc., and the detected impurities cannot include its decomposition products. The characteristic impurities are not satisfactory, and the detection limit is unsatisfactory, so it is a technical problem to effectively and quickly detect the C ₄ F ₇ N-CO ₂ mixed gas.

For the detection of impurities such as the decomposition products of C ₄ F ₇ N, the currently reported detection methods include Fourier transform infrared spectroscopy (FTIR), GC-MS, etc., and they are all simple detections with relatively few types of impurities. The system and method for detecting the decomposition products of C ₄ F ₇ N have not yet been reported.

SUMMARY OF THE INVENTION

In view of this, the present invention proposes a gas chromatographic detection system and method for measuring perfluoroisobutyronitrile gas components, aiming to solve the problem in the prior art for the detection of impurity components in C ₄ F ₇ N-CO ₂ mixed gas. The problem of low detection efficiency during detection.

In one aspect, the present invention provides a gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, comprising: a first analysis unit and a second analysis unit; the first analysis unit includes a first switch connected in sequence a valve, a third chromatographic column, a third switching valve and a first detector; the first interface on the first switching valve is connected to the gas sample source to be measured; the third switching valve is provided with a second vent valve; The second analysis unit includes a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector connected in sequence; the first interface on the second switching valve is connected to the gas to be measured The sample source is connected; the second switching valve is provided with a third venting valve; the fourth switching valve is provided with a fourth venting valve.

Further, in the above-mentioned gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, the first carrier gas is connected to the fifth interface of the first switching valve; the gas sample inlet to be tested is connected to the first switching valve. The first interface of the first switching valve is connected to the first interface of the second switching valve; the third interface of the first switching valve is connected to the sixth interface of the first switching valve The connected pipeline is provided with a first quantitative pipe; the fourth interface of the first switching valve is connected with the first end of the third chromatographic column.

Further, in the above-mentioned gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, the fourth carrier gas is connected to the fourth interface of the second switching valve, and the third carrier gas is connected to the second switching valve. The seventh port is connected; the third vent valve is connected with the eighth port of the second switching valve, the gas sample outlet to be tested is connected with the second port of the second switching valve; the third port of the second switching valve is connected A second quantitative pipe is provided on the pipeline connecting the three ports with the tenth port of the second switching valve; the pipeline connecting the fifth port of the second switching valve and the ninth port of the second switching valve is provided with The first chromatographic column is provided; the second chromatographic column is provided on the pipeline connecting the sixth interface of the second switching valve and the sixth interface of the fourth switching valve.

Further, in the above-mentioned gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, the second carrier gas is connected to the third interface of the third switching valve, and the second vent valve is connected to the third switching valve. the first port of the valve is connected, the first detector is connected with the fifth port of the third switching valve; the other end of the third chromatographic column is connected with the sixth port of the third switching valve; the The second port of the third switching valve is connected to the fourth port of the third switching valve.

Further, in the above-mentioned gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, the fifth carrier gas is connected to the third interface of the fourth switching valve, and the fourth vent valve is connected to the third port of the fourth switching valve. The first interface of the four switching valve is connected, the second detector is connected with the fifth interface of the fourth switching valve; the second interface of the fourth switching valve is connected with the fourth interface of the fourth switching valve .

Further, in the above gas chromatography detection system for measuring perfluoroisobutyronitrile gas components, the first detector and the second detector are both pulsed helium ionization detectors.

Further, in the above-mentioned gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition, the first switching valve, the third switching valve and the fourth switching valve are six-way purge pneumatic switching valves, The second switching valve is a ten-way purge pneumatic switching valve.

Further, in the above-mentioned gas chromatographic detection system for measuring perfluoroisobutyronitrile gas components, the first chromatographic column is a C4F7N special analysis pre-column; the second chromatographic column is a C4F7N special analysis column, and the third The chromatographic column is a capillary column for fluorocarbon analysis.

In the present invention, only one instrument can realize the accurate analysis of all components of the decomposition products of the C ₄ F ₇ N-CO ₂ mixed gas, which is beneficial to accurately determine the operation status of the electrical equipment; meanwhile, labor is saved It also reduces the investment cost of the instrument, which greatly reduces the cost of use, and correspondingly reduces the maintenance cost of the instrument; in addition, using one instrument for analysis can reduce the amount of sampling, the amount of sample gas used, and the amount of sample gas after use. Processing capacity, more safety and environmental protection.

On the other hand, the present invention also proposes a gas chromatographic analysis method for measuring perfluoroisobutyronitrile gas components, comprising the following steps: step (1), the first switching valve is injected by means of valve injection, and after After most of the fluorocarbons in the C ₄ F ₇ N-CO ₂ mixed gas in the first quantitative tube are separated by the third chromatographic column, the third switching valve is switched to switch the separated fluorocarbons to the first detection In step (2), the second switching valve adopts the method of backflushing and sampling, and the C ₄ F ₇ N-CO ₂ mixed gas passing through the second quantitative tube first passes through the first chromatographic column to realize the test to be detected. Pre-separation of gas samples, so that Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ first enter the second chromatographic column, and then switch the second switching valve to backflush other impurity components obtained by pre-separation; switch the fourth switching valve The impurity components Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ separated by the second chromatographic column are respectively switched to the second detector to respond to peaks.

Further, in the above-mentioned method for analyzing perfluoroisobutyronitrile gas components, the sample introduction step is as follows:

The first switching valve is switched, and the first carrier gas carries the gas sample to be measured in the first quantitative tube into the third chromatographic column, and at the same time, the flow is split through the three-way and the first vent valve, and the third chromatographic column is separated. In the three chromatographic columns, the substances with peaks before C ₃ F ₈ are vented through the second vent valve; the third switching valve is switched, so that C ₃ F ₈ and the impurity components after it enter the first detector respectively to emit peaks; After the C ₂ F ₅ CN peak is completed, the third switching valve is switched back to the initial state, and the C ₄ F ₇ N is vented;

The second switching valve and the fourth switching valve are switched, and the fourth carrier gas carries the gas sample to be measured in the second quantitative tube into the first chromatographic column. When C ₂ in the first chromatographic column The second switching valve is switched after F ₆ and the substance whose peak is before C ₂ F ₆ enters the second chromatographic column, so that the substance whose peak is after C ₂ F ₆ is backflushed and vented through the third vent valve; The third carrier gas carries the impurities separated from the second chromatographic column into the second detector to complete the peak output. After the CF4 peak is completed, the _fourth switching valve is switched so that the fourth vent valve is vented. When After the CO ₂ is completely vented, the fourth switching valve is switched back to the initial state, so that the C ₂ F ₆ peaks.

The method for analyzing perfluoroisobutyronitrile gas components provided by the invention can complete the analysis of various impurities in the C ₄ F ₇ N-CO ₂ mixed gas through one sample injection, and avoid instrument and human errors introduced by multiple sample injections , which improves the accuracy of the analysis and the analysis time is short, which is beneficial for the relevant electrical equipment users to timely and accurately judge the operation status of the electrical equipment according to the analysis results and take corresponding safety measures in time.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be considered limiting of the invention. Also, the same components are denoted by the same reference numerals throughout the drawings. In the attached image:

Fig. 1 is the connection structure schematic diagram of the gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition provided by the embodiment of the present invention;

Fig. 2 is the schematic flow chart of the first switching valve sampling in the embodiment of the present invention, shunting through the three-way and the first vent valve, and venting CO ₂ through the second vent valve;

FIG. 3 is a schematic flow chart showing that impurities such as C ₃ F ₈ enter the first detector and simultaneously vent C ₄ F ₇ N through a third switching valve in an embodiment of the present invention;

Fig. 4 shows that the fourth carrier gas carries the sample in the second quantitative tube into the first chromatographic column, and all the C ₂ F ₆ and the substances with peaks before C ₂ F ₆ in the first chromatographic column enter the first chromatographic column. Schematic flow chart of separation by two chromatographic columns;

Fig. 5 is the schematic flow chart of venting and backflushing the substance behind C ₂ F ₆ through the third vent valve in the embodiment of the present invention;

6 is a chromatographic analysis diagram of each impurity gas component in the first detector in the embodiment of the present invention;

FIG. 7 is a chromatographic analysis diagram of each impurity gas component in the second detector in the embodiment of the present invention.

In the figure: 1- the first switching valve; 2- the second switching valve; 3- the third switching valve; 4- the fourth switching valve; 5- the first chromatographic column; 6- the second chromatographic column; 7- the third chromatographic column Column; 8-first carrier gas; 9-second carrier gas; 10-third carrier gas; 11-fourth carrier gas; 12-fifth carrier gas; 13-first quantitative tube; 14-second quantitative Tube; 15-Gas sample inlet to be tested; 16-Gas sample outlet to be tested; 17-First vent valve; 18-Second vent valve; 19-Third vent valve; 20-Fourth vent valve; 21-Tee ; 22 - the first detector; 23 - the second detector.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly understood, and will fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Referring to FIG. 1 , a gas chromatography detection system for measuring perfluoroisobutyronitrile gas components according to an embodiment of the present invention includes: a first analysis unit and a second analysis unit; wherein the first analysis unit includes a first switching valve connected in sequence 1. The third chromatographic column 7, the third switching valve 3 and the first detector 22; the first interface on the first switching valve 1 is connected to the gas sample source to be measured; the third switching valve 3 is provided with a The second vent valve 18 .

The second analysis unit includes a second switching valve 2 , a first chromatographic column 5 , a second chromatographic column 6 , a fourth switching valve 4 and a second detector 23 connected in sequence; the first interface on the second switching valve 2 201 is connected to the gas sample source to be tested; the second switching valve 2 is provided with a third vent valve 19 ; the fourth switching valve 4 is provided with a fourth vent valve 20 .

Specifically, the gas to be measured in the present invention is a C ₄ F ₇ N-CO ₂ mixed gas. In this embodiment, the first analysis unit is used to measure the C ₃ F ₈ in the decomposition product of the C ₄ F ₇ N-CO ₂ mixed gas. (Octafluoropropane), C ₂ HF ₅ Cl (R125), C ₂ H ₃ F ₃ (R143a), C ₂ H ₂ F ₄ (R134a), C ₃ F ₆ (hexafluoropropene) and C ₂ F ₅ CN The content of Air, CO, CF ₄ and C ₂ F ₆ in the decomposition product in the C ₄ F ₇ N-CO ₂ mixed gas was determined by the second analysis unit. The interfaces of the first switching valve 1 , the third chromatographic column 7 , the third switching valve 3 and the corresponding interfaces are connected with the first detector 22 through gas pipelines; the second switching valve 2 , the first chromatographic column 5 , the second chromatographic column 6 , each interface on the fourth switching valve 4 and the corresponding interface and the second detector 23 are all connected by gas pipelines. The second vent valve 18, the third vent valve 19 and the fourth vent valve 20 may all be needle valves.

Preferably, the first switching valve 1, the third switching valve 3 and the fourth switching valve 4 are six-way purging pneumatic switching valves, and the second switching valve 2 is a ten-way purging pneumatic switching valve . By reasonably switching each switching valve, the process of chromatographic analysis can be effectively simplified, the time of chromatographic analysis can be shortened, and the work efficiency of chromatographic analysis can be greatly improved.

Preferably, the first chromatographic column 5 is a special analysis pre-column for C ₄ F ₇ N, for example, a high-polarity molecular column (strong and medium-polar molecular columns) can be used, so that air, C ₂ Pre-separation of F ₆ , etc. and C ₄ F ₇ N; the second chromatographic column 6 is a special analysis column for C ₄ F ₇ N, for example, a molecular sieve chromatographic column can be used to realize air, CO, CF ₄ , CO ₂ and C ₂ For the separation of F ₆ , the third chromatographic column 7 is a capillary column for analyzing fluorocarbon compounds, which is used for C ₄ F ₇ N decomposition products C ₃ F ₈ (octafluoropropane), C ₂ HF ₅ Cl (R125), C _{2 H3F3} ( _R143a ), _C2H2F4 ( _R134a ), _{C3F6 ( hexafluoropropene} ) and _{C2F5CN were} isolated. Selecting a suitable column can separate specific impurity components and avoid interference between impurities.

The first detector 22 and the second detector 23 can both be pulsed helium ionization detectors, which ensures high analytical sensitivity and can make the detection limit of all components reach 50ppb.

In order to flexibly control the first analysis unit, preferably, the first carrier gas 8 is connected to the fifth interface of the first switching valve 1; the first interface of the first switching valve 1 is connected to the gas sample inlet 15 to be measured; the The second port 102 of the first switching valve 1 is connected to the first port 201 of the second switching valve 2 , that is, the second switching valve 2 is connected to the to-be-waited valve through the second port of the first switching valve 1 . Connect the gas sample line. A first quantitative pipe 13 is provided on the pipeline connecting the third port 103 of the first switching valve 1 with the sixth port 106 of the first switching valve 1 ; the fourth port 104 of the first switching valve 1 connected with the first end of the third chromatographic column 7 .

Preferably, a flow dividing unit is provided between the first switching valve 1 and the third chromatographic column 7 . More specifically, the flow splitting unit includes: a three-way 21 and a first vent valve 17; wherein, one end of the three-way communicates with the second end of the third chromatographic column, and the other end of the three-way 21 is connected to the The first vent valve 17 is communicated. That is, a tee 21 is provided on the pipeline connecting the first switching valve 1 and the third chromatographic column 7 , and the other end of the tee 21 is connected with the first vent valve 17 . It should be noted that the first end of the third chromatographic column 7 may be the inlet end, and the second end may be the outlet end.

In this embodiment, the first quantitative tube 13 is arranged on the first switching valve 1, which can precisely control the amount of the sample, so as to better save the amount of the sample. The first vent valve 17 may be a needle valve.

The specification of the tee 21 matches the capillary column interface in the third chromatographic column 7, and the dedicated capillary column interface tee 21 reduces the dead volume, reduces the noise, and effectively avoids air interference. The flow is split through the three-way 21 and the first vent valve 17, so as to prevent the content of the gas sample to be tested in the third chromatographic column 7 from being too high, which is beneficial to prolong the life of the capillary column of the third chromatographic column 7, and reduces the The interference problem of tailing of the main peak in the third chromatographic column 7.

The second carrier gas 9 is connected to the third port 33 of the third switching valve 3 , the second vent valve 18 is connected to the first port 31 of the third switching valve 3 , the first detector 22 is connected to The fifth port 35 of the third switching valve 3 is connected; the other end of the third chromatographic column 7 is connected to the sixth port 36 of the third switching valve 3 ; the second port of the third switching valve 3 32 is connected to the fourth port 34 of the third switching valve 3 . This process design ensures the venting of C ₄ F ₇ N and CO ₂ , which can effectively prevent the main peak from entering the first detector 22 and affect the analysis of impurity content.

In order to flexibly control the second analysis unit, preferably, the fourth carrier gas 11 is connected to the fourth port 204 of the second switching valve 2 , and the third carrier gas 10 is connected to the seventh port 207 of the second switching valve 2 . ; The third vent valve 19 is connected to the eighth port 208 of the second switching valve 2, and the gas sample outlet 16 to be tested is connected to the second port 202 of the second switching valve 2; the second switching valve A second quantitative pipe 14 is provided on the pipeline connecting the third port 203 of the second switching valve 2 with the tenth port 210 of the second switching valve 2; the fifth port 205 of the second switching valve 2 is connected to the second switching valve 2 The first chromatographic column 5 is provided on the pipeline connected to the ninth interface 209 of the 2; the pipeline connected with the sixth interface 206 of the second switching valve 2 and the sixth interface 46 of the fourth switching valve 4 There is the second chromatography column 6 . This backflushing process design avoids C ₄ F ₇ N from entering the second detector 23 and shortens the analysis time. Wherein, in the detection process, in order to realize the flexibility of the backflushing operation, it is preferable to use the fourth inlet of the second switching valve 2 as the backflushing gas inlet. Setting the second quantitative tube 14 on the second switching valve 2 can precisely control the amount of the sample, so as to better save the amount of the sample.

The fifth carrier gas 12 is connected to the third port 43 of the fourth switching valve 4 , the fourth vent valve 20 is connected to the first port 41 of the fourth switching valve 4 , and the second detector 23 is connected to the fifth port 45 of the fourth switching valve 4 ; the second port 42 of the fourth switching valve 4 is connected to the fourth port 44 of the fourth switching valve 4 . This flow design prevents CO ₂ from entering the second detector 23 . The first carrier gas 8 , the second carrier gas 9 , the third carrier gas 10 , the fourth carrier gas 11 and the fifth carrier gas 12 used in this application are 99.999% high-purity helium gas.

It can be clearly drawn from the above that the gas chromatographic detection system provided in this embodiment for measuring the gas composition of perfluoroisobutyronitrile only needs one instrument to realize the detection of C ₄ F ₇ N-CO ₂ mixed gas decomposition products. Accurate analysis of all components is beneficial to accurately determine the operating status of electrical equipment; at the same time, labor and testing time are saved, instrument investment costs are also reduced, the use cost is greatly reduced, and the instrument maintenance cost is correspondingly reduced. ; In addition, the use of one instrument for analysis can reduce the amount of sampling, the amount of sample gas used and the amount of sample processing after use, which is safer and more environmentally friendly.

Method example:

The steps of the method for analyzing the composition of perfluoroisobutyronitrile gas provided in the embodiment of the present invention are as follows:

In step S1, the first switching valve is injected by means of valve injection, and most of the fluorocarbons in the C ₄ F ₇ N-CO ₂ mixed gas passing through the first quantitative tube are separated by the third chromatographic column, and then switched. The third switching valve 3 switches the separated fluorocarbon to the first detector to respond to a peak. Most of the fluorocarbons here include C ₃ F ₈ (octafluoropropane), C ₂ HF ₅ Cl (R125), C ₂ H ₃ F ₃ (R143a), C ₂ H ₂ F ₄ (R134a), C ₃ F ₆ (hexafluoropropene) and C ₂ F ₅ CN.

The specific injection process in this step is as follows:

Referring to FIG. 2, the first switching valve 1 is switched, and the first carrier gas 8 carries the gas sample to be measured in the first quantitative tube 13 into the third chromatographic column 7, and simultaneously passes through the tee and the first vent. The valve is used for splitting, and the substances in the third chromatographic column whose peaks are before C ₃ F ₈ are vented through the second vent valve. The species whose peaks are before C ₃ F ₈ here mainly refers to CO ₂ . When switching the first switching valve 1, the first carrier gas 8 is connected to the fifth port 105 of the first switching valve, and at the same time, the fifth port 105, the sixth port 106 and the first quantitative tube 13 of the first switching valve 1 , the third interface 103, the fourth interface 104, the tee 21 and the third chromatographic column 7, the sixth interface 36 and the first interface 31 of the third switching valve 3 are connected in sequence, and the first interface 31 of the third switching valve is connected with the first interface 31 of the third switching valve. One end of the two venting valves 18 is connected, so that the components that do not need to be analyzed (mainly C ₄ F ₇ N) are vented through the second venting valve.

Referring to FIG. 3 , switch the third switching valve 3 so that C ₃ F ₈ and the impurity components after it enter the first detector 22 for peak output respectively; after the C ₂ F ₅ CN peak is completed, switch The third switching valve 3 returns to the initial state, and the C ₄ F ₇ N is vented, and the analysis work of the first analysis unit is ended. in:

When switching the third switching valve 3, the third chromatographic column 7, the sixth interface 36 of the third switching valve 3 and the inlet of the first detector 22 are connected in sequence, so that C ₃ F ₈ and the impurity group whose peaks are after it into the first detector 22. Switch the third switching valve 3 back to the initial state, that is, the sixth port 36 of the third switching valve 3 is connected to the first port 31, the first port 31 is connected to one end of the second vent valve 18, and the third port 33 is connected to the first port 31. The second port 32 is connected, and the fourth port 34 is connected to the fifth port 35 , so that the C ₄ F ₇ N separated from the third chromatographic column 7 is vented. So far, the analytical spectrum shown in Fig. 6 can be obtained, and Fig. 6 is about 50 ppm of C ₃ F ₈ (octafluoropropane), C ₂ HF ₅ Cl (R125), C ₂ H ₃ F ₃ (R143a), C Standard gas spectra for ₂ H ₂ F ₄ (R134a), C ₃ F ₆ (hexafluoropropene) and C ₂ F ₅ CN.

In step S2, the second switching valve 2 adopts the method of backflushing and sampling, and the C ₄ F ₇ N-CO ₂ mixed gas passing through the second quantitative tube first passes through the first chromatographic column to realize the pre-separation of the gas sample to be measured, so that Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ first enter the second chromatographic column, and then switch the second switching valve to backflush other impurity components obtained by pre-separation; switch the fourth switching valve to remove the second chromatographic column The separated impurity components Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ are respectively switched to the second detector to respond to peaks.

The specific injection process in this step is as follows:

4, switch the second switching valve 2 and the fourth switching valve 4, the fourth carrier gas 11 carries the gas sample to be measured in the second quantitative tube 14 into the first chromatographic column 5, see Fig. 5, when the C ₂ F ₆ in the first chromatographic column 5 and the substances whose peaks are before C ₂ F ₆ enter the second chromatographic column 6, the second switching valve 2 is switched, so that the peaks are at C The substances after ₂ F ₆ are backflushed and vented through the third vent valve 19; at the same time, the third carrier gas 10 carries the remaining impurities separated from the second chromatographic column 6 into the second detector 23 to complete the peak output; refer to FIG. 1 , when the peak of CF ₄ is completed, switch the fourth switching valve 4 so that CO ₂ is vented through the fourth vent valve 20, referring to FIG. 5, when the CO ₂ is completely vented, switch the fourth switching valve 4, so that C ₂ F ₆ out. The impurity gas components analyzed in the second detector 23 are air, CO, CF ₄ and C ₂ F ₆ .

Referring to FIG. 4 , when the second switching valve 2 is switched for the first time, the fourth carrier gas 11 is connected to the fourth port of the second switching valve 2 and enters the second quantitative tube 14 through the third port 203 of the second switching valve 2 , after carrying the C ₄ F ₇ N-CO ₂ mixed gas in the second quantitative tube 14 into the first chromatographic column 5 through the tenth interface 210 and the ninth interface 209 in turn for separation, so that the peak at C ₂ F ₆ The previous substance enters the second chromatographic column 6 through the outlet of the first chromatographic column 5 , the fifth port 205 and the sixth port 206 of the second switching valve 2 .

Referring to FIG. 5 , when the second switching valve 2 is switched for the second time, the fourth carrier gas 11 is connected to the fourth port 204 of the second switching valve 2 , so that the peak carried by the fourth carrier gas 11 is behind C ₂ F ₆ The substances are vented through the fifth port 205 , the first chromatographic column 5 , the ninth port 209 , the eighth port 208 , and the third vent valve 19 connected to the eighth port 208 in sequence. At the same time, the third carrier gas 10 is connected to the seventh interface of the second switching valve 2, and at the same time, the fourth switching valve 4 is switched, so that the outlet of the second chromatographic column 6, the sixth interface 46 of the fourth switching valve 4, the fifth The interface 45 and the second detector 23 are connected in sequence, so that the impurity components separated from the first chromatographic column 5 are carried to the second chromatographic column 6 for separation, and finally carried to the second detector 23 .

Referring to FIG. 1 again, after the peaking of CF ₄ is completed, the fourth switching valve 4 is switched, so that the sixth port of the fourth switching valve 4 is connected to the first port, and the first port is connected to one end of the fourth vent valve 20, so as to The CO ₂ is vented through the fourth vent valve 20 . Referring to FIG. 5, after the CO ₂ is emptied, switch the fourth switching valve 4 again to switch the second chromatographic column 6, the sixth interface and the fifth interface of the fourth switching valve 4 to the second detector 23, such that C ₂ F ₆ peaks; finally switch the fourth switching valve 4 to return to the state shown in Figure 1, the analysis is over, and the analysis spectrum shown in Figure 7 is obtained. Figure 7 is 160ppm of air, about 50ppm of CO, CF Standard gas spectra of ₄ and C ₂ F ₆ .

The above steps S1 and S2 can be performed at the same time to realize one sample injection. By reasonably switching the switching valves in each analysis unit, the process of chromatographic analysis is simplified, the interference between impurities is effectively avoided, and the detection limit of each impurity component is It can reach 50ppb, realizing the full analysis of impurities in C ₄ F ₇ N-CO ₂ mixed gas.

It can be seen that the present invention can complete the analysis of various impurities in the C ₄ F ₇ N-CO ₂ mixed gas through one sample injection, avoid instrumental and human errors introduced by multiple sample injections, and improve the accuracy of analysis and analysis. The time is short, which is beneficial for the relevant electrical equipment users to timely and accurately judge the operation status of the electrical equipment according to the analysis results, and then take corresponding safety measures in time.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (10)

1. a gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition, is characterized in that, comprises: a first analysis unit, which includes a first switching valve, a third chromatographic column, a third switching valve and a first detector connected in sequence; the first interface on the first switching valve is connected to the gas sample source to be measured; the The third switching valve is provided with a second vent valve; The second analysis unit includes a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector connected in sequence; the first interface on the second switching valve is connected to the gas to be measured The sample source is connected; the second switching valve is provided with a third venting valve; the fourth switching valve is provided with a fourth venting valve. 2. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the first carrier gas is connected with the fifth interface of the first switching valve; the gas sample to be measured The inlet is connected to the first port of the first switching valve; the second port of the first switching valve is connected to the first port of the second switching valve; the third port of the first switching valve is connected to the The pipeline connected to the sixth port of the first switching valve is provided with a first quantitative tube; the fourth port of the first switching valve is connected to the first end of the third chromatographic column. 3. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the fourth carrier gas is connected with the fourth interface of the second switching valve, and the third carrier gas is is connected with the seventh port of the second switching valve; the third vent valve is connected with the eighth port of the second switching valve, and the gas sample outlet to be tested is connected with the second port of the second switching valve; A second quantitative pipe is provided on the pipeline connecting the third port of the second switching valve with the tenth port of the second switching valve; the fifth port of the second switching valve is connected to the second switching valve. The first chromatographic column is provided on the pipeline connected with the ninth interface; the second chromatographic column is provided on the pipeline connected with the sixth interface of the second switching valve and the sixth interface of the fourth switching valve. 4. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the second carrier gas is connected to the third interface of the third switching valve, and the second carrier gas is connected to the third interface of the third switching valve. The vent valve is connected to the first interface of the third switching valve, the first detector is connected to the fifth interface of the third switching valve; the other end of the third chromatographic column is connected to the third switching valve The sixth port of the third switching valve is connected; the second port of the third switching valve is connected to the fourth port of the third switching valve. 5. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the fifth carrier gas is connected with the third interface of the fourth switching valve, and the The fourth vent valve is connected to the first interface of the fourth switching valve, the second detector is connected to the fifth interface of the fourth switching valve; the second interface of the fourth switching valve is connected to the first interface of the fourth switching valve. The fourth interface of the four switching valve is connected. 6. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the first detector and the second detector are both pulsed helium ionization detectors . 7. The gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition according to claim 1, wherein the first switching valve, the third switching valve and the fourth switching valve are A six-way purging pneumatic switching valve, the second switching valve is a ten-way purging pneumatic switching valve. 8 . The gas chromatography detection system for measuring perfluoroisobutyronitrile gas components according to claim 1 , wherein the first chromatographic column is a special analysis pre-column for C ₄ F ₇ N; the second The chromatographic column is a special C ₄ F ₇ N analytical column, and the third chromatographic column is a fluorocarbon analytical capillary column. 9. a method utilizing gas chromatography detection system as described in any one of claim 1 to 8 to analyze perfluoroisobutyronitrile gas composition, is characterized in that, comprises the following steps: In step (1), the first switching valve is injected by means of valve injection, and most of the fluorocarbons in the C ₄ F ₇ N-CO ₂ mixed gas passing through the first quantitative tube are separated by the third chromatographic column. , switching the third switching valve to switch the separated fluorocarbon to the first detector to respond to a peak; In step (2), the second switching valve adopts the method of backflushing and sampling, and the C ₄ F ₇ N-CO ₂ mixed gas passing through the second quantitative tube first passes through the first chromatographic column to realize the pre-separation of the gas sample to be measured, Make Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ enter the second chromatographic column first, then switch the second switching valve to backflush other impurity components obtained by pre-separation; switch the fourth switching valve to separate the second chromatographic column The impurity components Air, CO, CF ₄ , CO ₂ and C ₂ F ₆ separated by the column are respectively switched to the second detector to respond to the peaks. 10. the method for analyzing perfluoroisobutyronitrile gas composition according to claim 9, is characterized in that, described sample introduction step is as follows: The first switching valve is switched, and the first carrier gas carries the gas sample to be measured in the first quantitative tube into the third chromatographic column, and at the same time, the flow is split through the three-way and the first vent valve, and the third chromatographic column is separated. In the three chromatographic columns, the substances with peaks before C ₃ F ₈ are vented through the second vent valve; the third switching valve is switched, so that C ₃ F ₈ and the impurity components after it enter the first detector respectively to emit peaks; After the C ₂ F ₅ CN peak is completed, the third switching valve is switched back to the initial state, and the C ₄ F ₇ N is vented; The second switching valve and the fourth switching valve are switched, and the fourth carrier gas carries the gas sample to be measured in the second quantitative tube into the first chromatographic column. When C ₂ in the first chromatographic column The second switching valve is switched after F ₆ and the substance whose peak is before C ₂ F ₆ enters the second chromatographic column, so that the substance whose peak is after C ₂ F ₆ is backflushed and vented through the third vent valve; The third carrier gas carries the impurities separated from the second chromatographic column into the second detector to complete the peak output. After the CF4 peak is completed, the _fourth switching valve is switched so that the fourth vent valve is vented. When the CO ₂ is completely vented, the fourth switching valve is switched back to the initial state, so that the C ₂ F ₆ peaks.

Images