CN111679025B - Gas chromatography detection system and method for measuring perfluoroisobutyronitrile gas component - Google Patents
Gas chromatography detection system and method for measuring perfluoroisobutyronitrile gas component Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 32
- AASDJASZOZGYMM-UHFFFAOYSA-N 2,3,3,3-tetrafluoro-2-(trifluoromethyl)propanenitrile Chemical compound FC(F)(F)C(F)(C#N)C(F)(F)F AASDJASZOZGYMM-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 238000004817 gas chromatography Methods 0.000 title claims abstract description 25
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000004458 analytical method Methods 0.000 claims abstract description 47
- 239000007789 gas Substances 0.000 claims description 88
- 239000012159 carrier gas Substances 0.000 claims description 41
- 239000012535 impurity Substances 0.000 claims description 33
- 239000000203 mixture Substances 0.000 claims description 15
- 238000002347 injection Methods 0.000 claims description 14
- 239000007924 injection Substances 0.000 claims description 14
- 239000000126 substance Substances 0.000 claims description 12
- 238000010926 purge Methods 0.000 claims description 10
- 238000000926 separation method Methods 0.000 claims description 10
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 claims description 9
- -1 CF 4 Inorganic materials 0.000 claims description 8
- 239000001307 helium Substances 0.000 claims description 5
- 229910052734 helium Inorganic materials 0.000 claims description 5
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 5
- 238000007664 blowing Methods 0.000 claims description 3
- 230000004044 response Effects 0.000 claims description 3
- 238000000354 decomposition reaction Methods 0.000 abstract description 10
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 238000004587 chromatography analysis Methods 0.000 description 7
- 230000008569 process Effects 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 4
- 238000013022 venting Methods 0.000 description 4
- HCDGVLDPFQMKDK-UHFFFAOYSA-N hexafluoropropylene Chemical group FC(F)=C(F)C(F)(F)F HCDGVLDPFQMKDK-UHFFFAOYSA-N 0.000 description 3
- 238000005070 sampling Methods 0.000 description 3
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011010 flushing procedure Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- QYSGYZVSCZSLHT-UHFFFAOYSA-N octafluoropropane Chemical compound FC(F)(F)C(F)(F)C(F)(F)F QYSGYZVSCZSLHT-UHFFFAOYSA-N 0.000 description 2
- 229960004065 perflutren Drugs 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 1
- 101000878457 Macrocallista nimbosa FMRFamide Proteins 0.000 description 1
- 229910018503 SF6 Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 1
- 229960000909 sulfur hexafluoride Drugs 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/88—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/88—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86
- G01N2030/8809—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86 analysis specially adapted for the sample
- G01N2030/8872—Integrated analysis systems specially adapted therefor, not covered by a single one of the groups G01N30/04 - G01N30/86 analysis specially adapted for the sample impurities
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention provides a gas chromatography detection system and a method for determining perfluoroisobutyronitrile gas components, wherein the gas chromatography detection system comprises the following steps: a first analysis unit and a second analysis unit; the first analysis unit comprises a first switching valve, a third chromatographic column, a third switching valve and a first detector which are sequentially connected; a first interface on the first switching valve is connected with a gas sample source to be detected; the third switching valve is provided with a second emptying valve. The second analysis unit comprises a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector which are sequentially connected; the first interface on the second switching valve is connected with a gas sample source to be detected; a third emptying valve is arranged on the second switching valve; the fourth switching valve is provided with a fourth emptying valve. The gas chromatography system provided by the invention can realize the accurate analysis of all components of the C 4F7N-CO2 mixed gas decomposition product by only one instrument, and is beneficial to accurately judging the running condition of electrical equipment according to the accurate analysis; at the same time, the time taken for analysis is shortened.
Description
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
Gas-insulated electrical equipment generally uses sulfur hexafluoride (SF 6) gas as an insulating medium, but because SF 6 has a strong greenhouse effect, its GWP value is about 23900 times that of CO 2, which hinders the green development of our country and even the global power grid. Therefore, the search for SF 6 to replace gas with electrical performance equivalent to that of the gas and friendly to the environment becomes a hot spot for research at home and abroad in recent years. In 2014, alston (ALSTOM) has screened a gas named Novec ™ 4710 from the U.S. 3M company refrigerant catalog (C 4F7N）.C4F7 N has insulation performance which is more than 2.2 times that of SF 6 under the same condition, and GWP (global warming potential) is far lower than that of SF 6 gas.
In the operation process of the electrical equipment, if the equipment fails, partial discharge and other phenomena may occur. Under discharge conditions, the C 4F7N-CO2 mixed gas can decompose to possibly generate a large amount of CF 3 free radicals, CN free radicals and CF free radicals, and the combination of the free radicals can generate complex chemical reactions to generate decomposition products such as CF 3 CN, and the running condition of the equipment can be deduced by detecting the impurity content. Currently, there is no detection method for a system of C 4F7N-CO2 mixed gas in the market, which generally uses a plurality of instruments to detect, such as TCD (thermal conductivity detector), FTIR, etc., but the detected impurities cannot include the characteristic impurities of the decomposition products, and the detection limit is also unsatisfactory, so that it is a technical problem to effectively and rapidly detect the C 4F7N-CO2 mixed gas.
For detecting impurities such as C 4F7 N decomposition products, the detection methods reported at present comprise Fourier infrared spectroscopy (FTIR), GC-MS and the like, simple detection is adopted, the impurity types are relatively few, and a system and a method for detecting the C 4F7 N decomposition products by singly adopting chromatography have not been reported.
Disclosure of Invention
In view of the above, the invention provides a gas chromatography detection system and a method for measuring perfluoroisobutyronitrile gas components, which aim to solve the problem of lower detection efficiency in the prior art when detecting impurity components in C 4F7N-CO2 mixed gas.
In one aspect, the present invention provides a gas chromatography detection system for determining the composition of perfluoroisobutyronitrile gas, comprising: a first analysis unit and a second analysis unit; the first analysis unit comprises a first switching valve, a third chromatographic column, a third switching valve and a first detector which are sequentially connected; a first interface on the first switching valve is connected with a gas sample source to be detected; a second emptying valve is arranged on the third switching valve; the second analysis unit comprises a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector which are sequentially connected; the first interface on the second switching valve is connected with a gas sample source to be detected; a third emptying valve is arranged on the second switching valve; and a fourth emptying valve is arranged on the fourth switching valve.
Further, in the gas chromatography detection system for measuring the perfluoroisobutyronitrile gas component, a first carrier gas is connected with a fifth interface of the first switching valve; the gas sample inlet to be detected is connected with a first interface of the first switching valve; the second interface of the first switching valve is connected with the first interface of the second switching valve; a first metering tube is arranged on a pipeline connected with a third interface of the first switching valve and a sixth interface of the first switching valve; the fourth port of the first switching valve is connected to the first end of the third chromatographic column.
Further, in the gas chromatography detection system for measuring the perfluoroisobutyronitrile gas component, a fourth carrier gas is connected to a fourth interface of the second switching valve, and a third carrier gas is connected to a seventh interface of the second switching valve; the third vent valve is connected with an eighth interface of the second switching valve, and the gas sample outlet to be tested is connected with a second interface of the second switching valve; a second metering tube is arranged on a pipeline connected with a third interface of the second switching valve and a tenth interface of the second switching valve; the first chromatographic column is arranged on a pipeline connected with the fifth interface of the second switching valve and the ninth interface of the second switching valve; the second chromatographic column is arranged on a pipeline connected with the sixth interface of the second switching valve and the sixth interface of the fourth switching valve.
Further, in the gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition, a second carrier gas is connected to a third port of the third switching valve, a second vent valve is connected to a first port of the third switching valve, and a first detector is connected to a fifth port of the third switching valve; the other end of the third chromatographic column is connected with a sixth interface of the third switching valve; the second interface of the third switching valve is connected with the fourth interface of the third switching valve.
Further, in the gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition, the fifth carrier gas is connected to the third port of the fourth switching valve, the fourth vent valve is connected to the first port of the fourth switching valve, and the second detector is connected to the fifth port 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 gas chromatography detection system for measuring perfluoroisobutyronitrile gas composition, the first detector and the second detector are both pulsed helium ionization detectors.
In the gas chromatography detection system for measuring the perfluoroisobutyronitrile gas composition, the first switching valve, the third switching valve and the fourth switching valve are six-way purge pneumatic switching valves, and the second switching valve is a ten-way purge pneumatic switching valve.
Further, in the gas chromatography detection system for measuring the perfluoroisobutyronitrile gas component, the first chromatographic column is a C4F7N dedicated analytical pre-column; the second chromatographic column is a C4F7N special analysis column, and the third chromatographic column is a fluorocarbon analysis capillary column.
In the invention, the accurate analysis of all components of the C 4F7N-CO2 mixed gas decomposition product can be realized by only one instrument, which is beneficial to accurately judging the running condition of the electrical equipment; meanwhile, labor force and test time are saved, the investment cost of the instrument is reduced, the use cost is greatly reduced, and the maintenance cost of the instrument is correspondingly reduced; in addition, the sampling amount can be reduced by adopting one instrument for analysis, the using amount of sample gas and the processing amount of the used samples are reduced, and the method is safer and more environment-friendly.
In another aspect, the present invention also provides a gas chromatographic method for determining the gas content of perfluoroisobutyronitrile, comprising the steps of: the method comprises the following steps that (1) a first switching valve adopts a valve sample injection mode to sample, most fluorocarbon compounds in the mixed gas passing through a first metering tube C 4F7N-CO2 are separated through a third chromatographic column, and then the third switching valve is switched to switch the separated fluorocarbon compounds into a first detector to respond to a peak; step (2), the second switching valve adopts a back-blowing sample injection mode, the mixed gas of C 4F7N-CO2 passing through the second quantitative pipe is subjected to pre-separation of a gas sample to be detected through the first chromatographic column, so that Air, CO, CF 4、CO2 and C 2F6 firstly enter the second chromatographic column, and then the second switching valve is switched to back-blow other impurity components obtained through the pre-separation; switching the fourth switching valve switches the impurity components Air, CO, CF 4、CO2 and C 2F6 separated by the second chromatographic column to the second detector, respectively, in response to the peak.
Further, in the above method for analyzing perfluoroisobutyronitrile gas composition, the sample injection step is as follows:
Switching the first switching valve, enabling a first carrier gas to carry a gas sample to be detected in the first metering tube to enter the third chromatographic column, and simultaneously shunting through a tee joint and a first emptying valve, and emptying substances with peaks before C 3F8 in the third chromatographic column through a second emptying valve; switching the third switching valve so that C 3F8 and the following impurity components respectively enter the first detector to generate peaks; after the peak of the C 2F5 CN is finished, switching the third switching valve to return to the initial state, and emptying the C 4F7 N;
Switching the second switching valve and the fourth switching valve, wherein a fourth carrier gas carries a gas sample to be detected in the second quantitative pipe to enter the first chromatographic column, and switching the second switching valve after a substance with a peak before C 2F6 and a peak before C 2F6 in the first chromatographic column enters the second chromatographic column, so that the substance with the peak after C 2F6 is blown back and discharged through a third discharge valve; and simultaneously, the third carrier gas carries impurities separated from the second chromatographic column and enters a second detector to finish peak emission, after CF 4 finishes peak emission, the fourth switching valve is switched to enable the fourth switching valve to be emptied through the fourth emptying valve, and when CO 2 is completely emptied, the fourth switching valve is switched to return to an initial state to enable C 2F6 to emit peak.
According to the method for analyzing the perfluoroisobutyronitrile gas component, provided by the invention, the analysis of various impurities in the C 4F7N-CO2 mixed gas can be completed through one sample injection, the instrument and human error caused by multiple sample injection are avoided, the analysis accuracy is improved, the analysis time is short, and the method is beneficial to timely and accurately judging the operation condition of the electric equipment according to the analysis result by related electric equipment users, so that corresponding safety measures are timely taken.
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 only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
FIG. 1 is a schematic diagram of a connection structure of a gas chromatography detection system for measuring perfluoroisobutyronitrile gas components according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of the embodiment of the invention in which the sampling of the first switching valve is completed, the flow is split by the tee joint and the first vent valve, and the CO 2 is vented by the second vent valve;
FIG. 3 is a schematic flow chart of the embodiment of the invention in which impurities such as C 3F8 enter the first detector and C 4F7 N is simultaneously vented through the third switching valve;
FIG. 4 is a schematic flow chart of a fourth carrier gas carrying a sample in a second metering tube into a first chromatographic column and all substances in the first chromatographic column before C 2F6 and the peak at C 2F6 enter the second chromatographic column for separation in an embodiment of the invention;
FIG. 5 is a schematic flow chart of the material after C 2F6 in the embodiment of the present invention, which is discharged by the third discharge valve;
FIG. 6 is a diagram showing chromatographic analysis of each impurity gas component in the first detector according to the embodiment of the present invention;
FIG. 7 is a chromatographic chart of the impurity gas components in the second detector according to the embodiment of the present invention.
In the figure: 1-a first switching valve; 2-a second switching valve; 3-a third switching valve; 4-a fourth switching valve; 5-a first chromatographic column; 6-a second chromatographic column; 7-a third chromatographic column; 8-a first carrier gas; 9-a second carrier gas; 10-a third carrier gas; 11-fourth carrier gas; 12-a fifth carrier gas; 13-a first metering tube; 14-a second metering tube; 15-a gas sample inlet to be measured; 16-a gas sample outlet to be measured; 17-a first vent valve; 18-a second vent valve; 19-a third vent valve; 20-fourth vent valve; 21-tee; 22-a first detector; 23-a second detector.
Detailed Description
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 to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
Referring to fig. 1, a gas chromatography detection system for determining a perfluoroisobutyronitrile gas composition according to an embodiment of the present invention includes: a first analysis unit and a second analysis unit; the first analysis unit comprises a first switching valve 1, a third chromatographic column 7, a third switching valve 3 and a first detector 22 which are sequentially connected; the first interface on the first switching valve 1 is connected with a gas sample source to be detected; the third switching valve 3 is provided with a second vent valve 18.
The second analysis unit comprises 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 which are connected in sequence; the first interface 201 on the second switching valve 2 is connected with a gas sample source to be tested; a third emptying valve 19 is arranged on the second switching valve 2; the fourth switching valve 4 is provided with a fourth vent valve 20.
Specifically, the gas to be measured in the invention is a mixed gas of C 4F7N-CO2, and the content of C 3F8 (hexafluoropropylene ）、C2HF5Cl（R125）、C2H3F3（R143a）、C2H2F4（R134a）、C3F6（) and C 2F5 CN in the decomposition product of the mixed gas of C 4F7N-CO2 is measured by a first analysis unit in the embodiment; the contents of Air, CO, CF 4 and C 2F6 in the decomposition products in the C 4F7N-CO2 mixed gas were measured by a second analysis unit. The interfaces of the first switching valve 1, the third chromatographic column 7 and 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 and the fourth switching valve 4 are connected with the corresponding interfaces and the second detector 23 through gas pipelines. The second purge valve 18, the third purge valve 19 and the fourth purge valve 20 may each be a needle valve.
Preferably, the first switching valve 1, the third switching valve 3 and the fourth switching valve 4 are six-way purge pneumatic switching valves, and the second switching valve 2 is a ten-way purge pneumatic switching valve. Through reasonable switching of each switching valve, the flow of chromatographic analysis can be effectively simplified, the chromatographic analysis time is shortened, and the work efficiency of chromatographic analysis is greatly improved.
Preferably, the first chromatographic column 5 is a C 4F7 N dedicated analytical pre-column, for example, a high-polarity molecular column (a strong-polarity and medium-polarity molecular column) can be used to pre-separate air, C 2F6, etc. and C 4F7 N; the second chromatographic column 6 is a special analytical column for C 4F7 N, for example, a molecular sieve chromatographic column can be adopted to separate air, CO, CF 4、CO2 and C 2F6, the third chromatographic column 7 is a fluorocarbon analysis capillary column, and separation is carried out on C 4F7 N decomposition products C 3F8 (octafluoropropane ）、C2HF5Cl（R125）、C2H3F3（R143a）、C2H2F4（R134a）、C3F6（ hexafluoropropylene) and C 2F5 CN. The selection of a suitable chromatographic column can be directed at specific impurity components for separation, avoiding interference between impurities.
The first detector 22 and the second detector 23 can be pulsed helium ionization detectors, which ensures high analysis sensitivity and can make the detection limit of all components reach 50ppb.
For flexible control of the first analysis unit, the first carrier gas 8 is preferably connected to the fifth interface of the first switching valve 1; the first interface of the first switching valve 1 is connected with a gas sample inlet 15 to be tested; the second port 102 of the first switching valve 1 is connected to the first port 201 of the second switching valve 2, i.e. the second switching valve 2 is connected to the gas sample line to be measured via the second port of the first switching valve 1. A first metering tube 13 is arranged on a pipeline connected with the third interface 103 of the first switching valve 1 and the sixth interface 106 of the first switching valve 1; the fourth port 104 of the first switching valve 1 is connected to the first end of the third chromatographic column 7.
Preferably, a split flow unit is disposed between the first switching valve 1 and the third chromatographic column 7. More specifically, the diverting unit includes: a tee 21 and a first vent valve 17; wherein one end of the tee is communicated with the second end of the third chromatographic column, and the other end of the tee 21 is communicated with the first emptying valve 17. That is, a tee joint 21 is arranged on a pipeline connected with the first switching valve 1 and the third chromatographic column 7, and the other end of the tee joint 21 is connected with a first emptying valve 17. The first end of the third chromatographic column 7 may be an inlet end, and the second end may be an outlet end.
In this embodiment, the first metering tube 13 is disposed on the first switching valve 1, so that the sample consumption can be precisely controlled, and the sample consumption can be better saved. The first blow-off valve 17 may be a needle valve.
The specification of tee bend 21 matches with the capillary column interface in the third chromatographic column 7, and special capillary column interface tee bend 21 has reduced dead volume, has reduced the noise, has effectively avoided the air to disturb. The three-way valve 21 and the first emptying valve 17 are used for shunting, so that the content of a gas sample to be detected entering the third chromatographic column 7 is prevented from being too high, the service life of a capillary column of the third chromatographic column 7 is prolonged, and the interference problem of main peak tailing in the third chromatographic column 7 is reduced.
The second carrier gas 9 is connected with a third port 33 of the third switching valve 3, the second purge valve 18 is connected with a first port 31 of the third switching valve 3, and the first detector 22 is connected with a fifth port 35 of the third switching valve 3; the other end of the third chromatographic column 7 is connected with a sixth interface 36 of the third switching valve 3; the second port 32 of the third switching valve 3 is connected to the fourth port 34 of the third switching valve 3. The process design ensures the emptying of C 4F7 N and CO 2, and can effectively avoid the main peak from entering the first detector 22 to influence the analysis of impurity content.
For flexible control of the second analytical unit, it is preferred that the fourth carrier gas 11 is connected to the fourth port 204 of the second switching valve 2 and that 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 with an eighth interface 208 of the second switching valve 2, and the gas sample outlet 16 to be tested is connected with a second interface 202 of the second switching valve 2; a second metering tube 14 is arranged on a pipeline connected with the third port 203 of the second switching valve 2 and the tenth port 210 of the second switching valve 2; the first chromatographic column 5 is arranged on a pipeline connected with the fifth interface 205 of the second switching valve 2 and the ninth interface 209 of the second switching valve 2; the second chromatographic column 6 is arranged on a pipeline connected with the sixth interface 206 of the second switching valve 2 and the sixth interface 46 of the fourth switching valve 4. This blowback flow design avoids C 4F7 N entering the second detector 23 and shortens analysis time. In the detection process, in order to achieve flexibility of the back-flushing operation, the fourth inlet of the second switching valve 2 is preferably used as a back-flushing air inlet. The second metering tube 14 is arranged on the second switching valve 2, so that the dosage of the sample can be accurately controlled, and the sample dosage can be better saved.
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 a fourth port 44 of the fourth switching valve 4. This flow scheme 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 the present application are 99.999% high purity helium gas.
The above clearly shows that the gas chromatography detection system for measuring the components of the perfluoroisobutyronitrile gas provided in the embodiment can accurately analyze all components of the decomposition product of the mixed gas of C 4F7N-CO2 by only one instrument, thereby being beneficial to accurately judging the operation condition of the electrical equipment; meanwhile, labor force and test time are saved, the investment cost of the instrument is reduced, the use cost is greatly reduced, and the maintenance cost of the instrument is correspondingly reduced; in addition, the sampling amount can be reduced by adopting one instrument for analysis, the using amount of sample gas and the processing amount of the used samples are reduced, and the method is safer and more environment-friendly.
Method embodiment:
The method for analyzing the perfluoroisobutyronitrile gas comprises the following steps:
In the step S1, a first switching valve adopts a valve sample injection mode to inject sample, most fluorocarbon compounds in the mixed gas passing through the C 4F7N-CO2 of the first metering tube are separated through a third chromatographic column, and then the third switching valve 3 is switched to switch the separated fluorocarbon compounds to a first detector to respond to the peak. Most fluorocarbons herein include C 3F8 (octafluoropropane ）、C2HF5Cl（R125）、C2H3F3（R143a）、C2H2F4（R134a）、C3F6（ hexafluoropropylene) and C 2F5 CN.
The specific sample injection process in the step is as follows:
Referring to fig. 2, the first switching valve 1 is switched, the first carrier gas 8 carries the gas sample to be measured in the first metering tube 13 to enter the third chromatographic column 7, and meanwhile, the gas sample is split by the tee joint and the first emptying valve, so that the substances with peaks before C 3F8 in the third chromatographic column are emptied by the second emptying valve. The material which peaks before C 3F8 here is mainly CO 2. When the first switching valve 1 is switched, the first carrier gas 8 is connected with the fifth interface 105 of the first switching valve, and meanwhile, the fifth interface 105, the sixth interface 106, the first metering tube 13, the third interface 103, the fourth interface 104, the tee 21, the third chromatographic column 7, the sixth interface 36 and the first interface 31 of the third switching valve 3 are sequentially connected, and the first interface 31 of the third switching valve is connected with one end of the second venting valve 18, so that components (mainly C 4F7 N) which do not need to be analyzed can be conveniently vented through the second venting valve.
Referring to fig. 3, the third switching valve 3 is switched such that C 3F8 and impurity components after the peak enter the first detector 22 to peak respectively; and after the peak of the C 2F5 CN is out, switching the third switching valve 3 to return to the initial state, and emptying the C 4F7 N until the analysis work of the first analysis unit is finished. Wherein:
When the third switching valve 3 is switched, the third chromatographic column 7, the sixth interface 36 of the third switching valve 3 and the inlet of the first detector 22 are sequentially connected, so that the impurity components of C 3F8 and the impurity components after the peak enter the first detector 22. The third switching valve 3 is switched back to the initial state, i.e., the state in which 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, the third port 33 is connected to the second port 32, and the fourth port 34 is connected to the fifth port 35, to vent the C 4F7 N separated from the third column 7. Thus, the analysis spectrum shown in FIG. 6 was obtained, and the graph of FIG. 6 shows the standard gas spectra of C 3F8 (hexafluoropropylene octafluoropropane ）、C2HF5Cl（R125）、C2H3F3（R143a）、C2H2F4（R134a）、C3F6（) and C 2F5 CN at about 50 ppm.
Step S2, the second switching valve 2 is used for carrying out back-blowing sample injection, the mixed gas passing through the C 4F7N-CO2 of the second quantitative pipe is subjected to pre-separation of a gas sample to be detected through the first chromatographic column, so that Air, CO, CF 4、CO2 and C 2F6 enter the second chromatographic column first, and then the second switching valve is switched to back-blow other impurity components obtained through the pre-separation; switching the fourth switching valve switches the impurity components Air, CO, CF 4、CO2 and C 2F6 separated by the second chromatographic column to the second detector, respectively, in response to the peak.
The specific sample injection process in the step is as follows:
Referring to fig. 4, the second switching valve 2 and the fourth switching valve 4 are switched, the fourth carrier gas 11 carries the gas sample to be detected in the second quantitative pipe 14 to enter the first chromatographic column 5, referring to fig. 5, after the substances with peak C 2F6 and peak before C 2F6 in the first chromatographic column 5 enter the second chromatographic column 6, the second switching valve 2 is switched, so that the substances with peak after C 2F6 are blown back and discharged through the third discharge valve 19; while 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; referring to fig. 1, after the CF 4 is completely emptied, the fourth switching valve 4 is switched to enable the CO 2 to be emptied through the fourth emptying valve 20, and referring to fig. 5, after the CO 2 is completely emptied, the fourth switching valve 4 is switched to enable the C 2F6 to be completely emptied. The impurity gas components analyzed in the second detector 23 are air, CO, CF 4, and C 2F6.
Referring to fig. 4, when the second switching valve 2 is switched for the first time, the fourth carrier gas 11 is connected with the fourth interface of the second switching valve 2, and enters the second quantitative pipe 14 through the third interface 203 of the second switching valve 2, and after the mixed gas carrying the C 4F7N-CO2 in the second quantitative pipe 14 sequentially enters the first chromatographic column 5 to be separated through the tenth interface 210 and the ninth interface 209, the substance with the peak before the C 2F6 enters the second chromatographic column 6 through the outlet of the first chromatographic column 5, the fifth interface 205 and the sixth interface 206 of the second switching valve 2.
Referring to fig. 5, when the second switching valve 2 is switched for the second time, after the fourth carrier gas 11 is connected with the fourth port 204 of the second switching valve 2, the substance with the peak of the fourth carrier gas 11 after C 2F6 is sequentially discharged through the fifth port 205, the first chromatographic column 5, the ninth port 209, the eighth port 208, and the third discharge valve 19 connected with the eighth port 208. Meanwhile, the third carrier gas 10 is connected to the seventh port of the second switching valve 2, and at the same time, the fourth switching valve 4 is switched such that the outlet of the second chromatographic column 6, the sixth port 46, the fifth port 45 and the second detector 23 of the fourth switching valve 4 are sequentially connected to carry the impurity components separated from the first chromatographic column 5 to the second chromatographic column 6 for separation, and finally to the second detector 23.
Referring again to fig. 1, after the CF 4 is out of peak, the fourth switching valve 4 is switched such 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 venting valve 20, so as to vent the CO 2 through the fourth venting valve 20. Referring to fig. 5, after the CO 2 is exhausted, the fourth switching valve 4 is switched again to connect the second chromatographic column 6, the sixth interface and the fifth interface of the fourth switching valve 4 with the second detector 23, so that the peak of C 2F6 is generated; finally, the fourth switching valve 4 is switched back to the state shown in fig. 1, and the analysis is completed, so that an analysis spectrum shown in fig. 7 is obtained, and fig. 7 is a standard gas spectrum of 160ppm of air, about 50ppm of CO, CF 4 and C 2F6.
The steps S1 and S2 can be carried out simultaneously to realize one sample injection, and through reasonably switching the switching valves in each analysis unit, the flow of chromatographic analysis is simplified, the interference among impurities is effectively avoided, the detection limit of each impurity component can reach 50ppb, and the full analysis of the impurities in the C 4F7N-CO2 mixed gas is realized.
According to the invention, analysis of various impurities in the C 4F7N-CO2 mixed gas can be completed through one sample injection, so that instruments and human errors caused by multiple sample injection are avoided, the analysis accuracy is improved, the analysis time is short, and the method is beneficial for relevant electrical equipment users to judge the operation condition of the electrical equipment timely and accurately according to the analysis result, so that corresponding safety measures are timely taken.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (8)
1. A gas chromatography detection system for determining the composition of perfluoroisobutyronitrile gas, comprising:
The first analysis unit comprises a first switching valve, a third chromatographic column, a third switching valve and a first detector which are sequentially connected; a first interface on the first switching valve is connected with a gas sample source to be detected; a second emptying valve is arranged on the third switching valve; the third chromatographic column is a fluorocarbon analysis capillary column; the first detector is a pulsed helium ionization detector;
The second analysis unit comprises a second switching valve, a first chromatographic column, a second chromatographic column, a fourth switching valve and a second detector which are sequentially connected; the first interface on the second switching valve is connected with a gas sample source to be detected; a third emptying valve is arranged on the second switching valve; a fourth emptying valve is arranged on the fourth switching valve; the first chromatographic column is a C 4F7 N special analysis column; the second chromatographic column is a C 4F7 N special analysis column; the second detector is a pulsed helium ionization detector;
The first carrier gas is connected with a fifth interface of the first switching valve; the second carrier gas is connected with a third interface of the third switching valve; the third carrier gas is connected with a seventh interface of the second switching valve; the fourth carrier gas is connected with a fourth interface of the second switching valve; and the fifth carrier gas is connected with the third interface of the fourth switching valve.
2. The gas chromatography detection system for determining perfluoroisobutyronitrile gas composition according to claim 1, wherein a gas sample inlet to be measured is connected to a first port of the first switching valve; the second interface of the first switching valve is connected with the first interface of the second switching valve; a first metering tube is arranged on a pipeline connected with a third interface of the first switching valve and a sixth interface of the first switching valve; 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 determining perfluoroisobutyronitrile gas composition according to claim 1, wherein a third carrier gas is connected to a seventh interface of the second switching valve; the third vent valve is connected with an eighth interface of the second switching valve, and the gas sample outlet to be tested is connected with a second interface of the second switching valve; a second metering tube is arranged on a pipeline connected with a third interface of the second switching valve and a tenth interface of the second switching valve; the first chromatographic column is arranged on a pipeline connected with the fifth interface of the second switching valve and the ninth interface of the second switching valve; the second chromatographic column is arranged on a 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 determining a perfluoroisobutyronitrile gas composition according to claim 1, wherein the second vent valve is connected to a first port of the third switching valve, and the first detector is connected to a fifth port of the third switching valve; the other end of the third chromatographic column is connected with a sixth interface of the third switching valve; the second interface of the third switching valve is connected with the fourth interface of the third switching valve.
5. The gas chromatography detection system for determining a perfluoroisobutyronitrile gas composition according to claim 1, wherein the fourth vent valve is connected to a first port of the fourth switching valve, and the second detector is connected to a fifth port of the fourth switching valve; the second interface of the fourth switching valve is connected with the fourth interface of the fourth switching valve.
6. The gas chromatography detection system for determining perfluoroisobutyronitrile gas composition according to claim 1, wherein the first switching valve, the third switching valve, and the fourth switching valve are six-way purge pneumatic switching valves, and the second switching valve is a ten-way purge pneumatic switching valve.
7. A method for analyzing a perfluoroisobutyronitrile gas composition using the gas chromatography detection system according to any one of claims 1 to 6, comprising the steps of:
The method comprises the following steps that (1) a first switching valve adopts a valve sample injection mode to sample, most fluorocarbon compounds in the mixed gas passing through a first metering tube C 4F7N-CO2 are separated through a third chromatographic column, and then the third switching valve is switched to switch the separated fluorocarbon compounds into a first detector to respond to a peak;
Step (2), the second switching valve adopts a back-blowing sample injection mode, the mixed gas of C 4F7N-CO2 passing through the second quantitative pipe is subjected to pre-separation of a gas sample to be detected through the first chromatographic column, so that Air, CO, CF 4、CO2 and C 2F6 firstly enter the second chromatographic column, and then the second switching valve is switched to back-blow other impurity components obtained through the pre-separation; switching the fourth switching valve switches the impurity components Air, CO, CF 4、CO2 and C 2F6 separated by the second chromatographic column to the second detector, respectively, in response to the peak.
8. The method for analyzing perfluoroisobutyronitrile gas composition according to claim 7, wherein the sample introduction step is as follows:
Switching the first switching valve, enabling a first carrier gas to carry a gas sample to be detected in the first metering tube to enter the third chromatographic column, and simultaneously shunting through a tee joint and a first emptying valve, and emptying substances with peaks before C 3F8 in the third chromatographic column through a second emptying valve; switching the third switching valve so that C 3F8 and the following impurity components respectively enter the first detector to generate peaks; after the peak of the C 2F5 CN is finished, switching the third switching valve to return to the initial state, and emptying the C 4F7 N;
Switching the second switching valve and the fourth switching valve, wherein a fourth carrier gas carries a gas sample to be detected in the second quantitative pipe to enter the first chromatographic column, and switching the second switching valve after a substance with a peak before C 2F6 and a peak before C 2F6 in the first chromatographic column enters the second chromatographic column, so that the substance with the peak after C 2F6 is blown back and discharged through a third discharge valve; and simultaneously, the third carrier gas carries impurities separated from the second chromatographic column and enters a second detector to finish peak emission, after CF 4 finishes peak emission, the fourth switching valve is switched to enable the fourth switching valve to be emptied through the fourth emptying valve, and when CO 2 is completely emptied, the fourth switching valve is switched to return to an initial state to enable C 2F6 to emit peak.
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| CN112697904B (en) * | 2020-12-11 | 2022-12-13 | 朗析仪器（上海）有限公司 | Impurity component analysis system for electronic gas fluoromethane |
| CN113341040A (en) * | 2021-06-04 | 2021-09-03 | 云南电网有限责任公司丽江供电局 | Insulation degradation detection method and system for heptafluoroisobutyronitrile mixed gas insulation equipment |
| CN113376276A (en) * | 2021-06-04 | 2021-09-10 | 云南电网有限责任公司丽江供电局 | Fault pre-judging method and system for heptafluoroisobutyronitrile mixed gas insulation equipment |
| CN114609283B (en) * | 2022-03-16 | 2023-10-27 | 国网安徽省电力有限公司电力科学研究院 | System and method for measuring decomposition products in perfluoroisobutyronitrile |
| CN114609281A (en) * | 2022-03-16 | 2022-06-10 | 国网安徽省电力有限公司电力科学研究院 | System and method for measuring content of impurity components in perfluoroisobutyronitrile |
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