CN111830155A - Device and method for detecting content of non-methane total hydrocarbons in ambient air - Google Patents
Device and method for detecting content of non-methane total hydrocarbons in ambient air Download PDFInfo
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- CN111830155A CN111830155A CN202010685981.3A CN202010685981A CN111830155A CN 111830155 A CN111830155 A CN 111830155A CN 202010685981 A CN202010685981 A CN 202010685981A CN 111830155 A CN111830155 A CN 111830155A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 164
- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 65
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000012080 ambient air Substances 0.000 title claims abstract description 12
- 238000001514 detection method Methods 0.000 claims abstract description 31
- 238000010438 heat treatment Methods 0.000 claims abstract description 28
- 238000005070 sampling Methods 0.000 claims abstract description 28
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 21
- 239000007789 gas Substances 0.000 claims description 100
- 239000012159 carrier gas Substances 0.000 claims description 90
- 239000003570 air Substances 0.000 claims description 45
- 239000003463 adsorbent Substances 0.000 claims description 16
- 238000002347 injection Methods 0.000 claims description 14
- 239000007924 injection Substances 0.000 claims description 14
- 238000007664 blowing Methods 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 6
- 239000013589 supplement Substances 0.000 claims 2
- 238000000926 separation method Methods 0.000 abstract description 3
- 230000035945 sensitivity Effects 0.000 abstract description 2
- 230000001502 supplementing effect Effects 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 238000009835 boiling Methods 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 description 2
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- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229930003658 monoterpene Natural products 0.000 description 1
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Classifications
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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
-
- 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
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
-
- 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
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/16—Injection
- G01N30/20—Injection using a sampling valve
-
- 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
- G01N30/60—Construction of the column
-
- 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
- G01N30/62—Detectors specially adapted therefor
- G01N30/64—Electrical detectors
- G01N30/68—Flame ionisation detectors
-
- 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
- G01N30/86—Signal analysis
- G01N30/8675—Evaluation, i.e. decoding of the signal into analytical information
- G01N30/8679—Target compound analysis, i.e. whereby a limited number of peaks is analysed
-
- 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
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/16—Injection
- G01N30/20—Injection using a sampling valve
- G01N2030/201—Injection using a sampling valve multiport valves, i.e. having more than two ports
Abstract
The invention discloses a device and a method for detecting the content of non-methane total hydrocarbons in ambient air. The invention separates the non-methane total hydrocarbon in the sample gas in advance by the arrangement of the pre-catcher, improves the separation efficiency and the detection precision, can obtain the content value of the non-methane total hydrocarbon and the methane at the same time, accelerates the total release of the non-methane by the heating device, narrows the sampling bandwidth and further improves the detection precision and the sensitivity.
Description
Technical Field
The application relates to the technical field of atmospheric environment detection equipment, in particular to a device and a method for detecting the content of non-methane total hydrocarbons in ambient air.
Background
Non-methane total hydrocarbons (NMHC) refers to all volatile hydrocarbons except methane, mainly C2-C8, which have great photochemical activity and are precursors for forming photochemical smog. The non-methane total hydrocarbons are of many types, the most abundant of which are terpene-based compounds released by natural plants, accounting for about 65% of the total NMHC, and the most prominent of which are isoprene and monoterpenes, which form photochemical oxidants and aerosol particles by photochemical reactions in urban and rural atmospheres. The human sources of NMHC are mainly gasoline combustion, incineration, solvent evaporation, petroleum evaporation and transport losses and waste extraction, these five categories account for about 96% of the man-made emission of hydrocarbons. When the concentration of non-methane hydrocarbon in the atmosphere exceeds a certain value, the non-methane hydrocarbon is not only harmful to human health, but also can generate photochemical smog under certain conditions through sunlight irradiation, thus causing harm to the environment and human beings. Therefore, it is necessary to monitor and control non-methane total hydrocarbons in areas such as ambient air and plant boundaries.
The method for measuring the non-methane total hydrocarbons of the environmental air (HJ 604- 2017) and the fixed pollution source (HJ 38-2017) for the environmental protection in China is a gas chromatography, the content of the non-methane total hydrocarbons is measured by using a differential method, namely the total hydrocarbon content and the methane content of the sample gas are respectively measured, and the content of the non-methane total hydrocarbons is obtained by subtracting the methane content from the total hydrocarbon content. The concentrations of methane and non-methane total hydrocarbons in ambient air are about 1.4ppmv and 50 ppmm, and when the content of non-methane total hydrocarbons is much less than the methane concentration, i.e., the methane concentration approaches the total hydrocarbon concentration, the difference subtraction method causes errors in the non-methane total hydrocarbon detection values to be superimposed. In a state where the concentration of the non-methane total hydrocarbons is very low, the data error of the non-methane total hydrocarbons may be very large, thereby causing inaccuracy in the detection value.
In recent years, a method for testing the content of non-methane total hydrocarbons by adopting a direct method has appeared, wherein the method adopts a column switching back-flushing gas chromatography to measure methane and non-methane total hydrocarbons, namely methane and non-methane total hydrocarbons are separated by multi-way valve switching and a chromatographic column. However, the method requires that the separation capacity of the chromatographic column is strong enough, and non-methane total hydrocarbons are also separated in the chromatographic column, so that the problems that the sample introduction bandwidth is too large, the peak shape of the non-methane total hydrocarbons is low, and the detection limit is too high are easily caused.
Disclosure of Invention
The invention aims to solve the problems of the prior art, the non-methane total hydrocarbon is detected by adopting a direct method, the problem of detection value error superposition caused by a difference subtraction method is solved, and the non-methane total hydrocarbon is firstly separated by arranging a pre-catcher, so that the problems of low peak shape and high detection limit of the non-methane total hydrocarbon are avoided.
The invention provides a device for detecting the content of non-methane total hydrocarbons in ambient air, which comprises: a multi-way sample injection valve, a carrier gas channel, a sample gas channel, a quantitative ring, a pre-trap, a chromatographic column, a gas flow controller and a detector;
the chromatographic column is a capillary column;
the pre-trap comprises a trapping pipe and a heating device, wherein the trapping pipe is internally provided with a non-methane total hydrocarbon adsorbent, and the heating device is arranged on the outer surface of the trapping pipe and is used for heating the trapping pipe;
the multi-way sample injection valve comprises a first carrier gas inlet, a second carrier gas inlet and a sample gas inlet; the multi-way sampling valve has two working states: the device comprises a load state and a sampling state, and can be switched between the load state and the sampling state;
when the multi-way sampling valve is in a load state, one path of carrier gas sequentially passes through the first carrier gas inlet and the collecting pipe and then enters the detector to form a first carrier gas channel; the other path of carrier gas sequentially passes through the second carrier gas inlet and the chromatographic column and then reaches the detector to form a second carrier gas channel; the sample gas sequentially passes through the sample gas inlet, the quantitative ring and the gas flow controller to form a first sample gas channel;
when the multi-way sampling valve is in a sampling state, one path of carrier gas sequentially passes through the first carrier gas inlet, the quantitative ring, the collecting pipe and the chromatographic column and then reaches the detector to form a third carrier gas channel; the other path of carrier gas is connected with the second carrier gas inlet and then reaches the detector to form a fourth carrier gas channel; the sample gas port is sequentially connected with the sample gas inlet and the gas flow controller to form a second sample gas channel.
In a preferred embodiment, the detection device further comprises an exhaust pump, and the exhaust pump is connected with the gas flow controller.
In a preferred embodiment, the collecting pipe comprises a first collecting pipe and a second collecting pipe which are connected with each other, and the multi-way sample injection valve is used for sequentially conveying the carrier gas to the first collecting pipe and the second collecting pipe after passing through the quantitative ring in a sampling state.
In a preferred embodiment, a weak adsorbent is arranged in the first collecting pipe, a strong adsorbent is arranged in the second collecting pipe, the weak adsorbent is Tenax TA and/or Tenax GR, and the strong adsorbent is an activated carbon adsorbent.
The first collecting pipe is used for collecting macromolecular non-methane total hydrocarbons, and the second collecting pipe is used for collecting small molecular non-methane total hydrocarbons; methane may pass through the first and second collection tubes to the chromatography column and be separated therein.
In a preferred embodiment, the heating means comprises a heating wire wound around the surface of the trap pipe.
In a preferred embodiment, the heating device is a hot air flow injection type heating device, and comprises a hot air source and a hot air flow injector which are connected with each other, and the nozzle of the hot air flow injector faces the collecting pipe.
Preferably, the nozzle of the hot gas flow injector is flat.
In a preferred embodiment, the pre-trap further comprises a condensing means comprising a source of cryogenic gas flow and a cryogenic gas flow ejector connected to each other, the jet of the cryogenic gas flow ejector being directed towards the trap header.
Preferably, the nozzle of the low-temperature gas flow ejector is flat.
Preferably, the hot gas stream injector is arranged perpendicular to the low temperature gas stream injector.
In a preferred embodiment, the device further comprises a gas block comprising a first gas block and a second gas block, the first gas block being disposed on the first carrier gas channel between the pre-trap and the detector; the second air resistor is arranged on the second carrier gas channel and between the carrier gas source and the second carrier gas inlet.
In a preferred embodiment, the device further comprises an air supplementing passage, wherein the air supplementing passage comprises an air supplementing source, the air supplementing source is connected between the first carrier gas inlet and the pre-trap through an air supplementing pipe, and an air supplementing control valve is arranged on the air supplementing pipe.
The air supply passage is used for increasing the flow of the back-blowing airflow in the back-blowing process and improving the flow rate of the back-blowing airflow.
In a preferred embodiment, the device further comprises a central processing unit which is used for controlling the switching of the multi-way sampling valve, the opening and closing of the exhaust pump and the opening and closing of the air supplementing control valve.
In a preferred embodiment, the surface of the collection pipe is provided with a temperature sensor, and the temperature sensor is connected with a central processing unit.
When the temperature of the collecting pipe reaches a preset value, the temperature sensor transmits a signal to the central processing unit, and the central processing unit sends an instruction to the heating device to stop heating.
In a preferred embodiment, the detector is a hydrogen flame ionization detector.
In a preferred embodiment, the multi-way valve is a ten-way valve.
The invention also provides a method for directly detecting the content of non-methane total hydrocarbons, which comprises the following steps:
s1 sample injection: the multi-way sample injection valve is in a load state, the carrier gas is divided into two paths, one path sequentially passes through the first carrier gas inlet, the pre-trap and the detector, and the other path sequentially passes through the second carrier gas inlet, the chromatographic column and the detector; the sample gas sequentially passes through the sample gas inlet, the quantitative pipe and the gas flow controller;
s2 sampling: switching the multi-way sampling valve to be in a sampling state, wherein the carrier gas flows through a first carrier gas inlet, a quantitative ring, a pre-trap, a chromatographic column and a detector; the pre-trap adsorbs non-methane populations in the gas passing through the pre-trap, and the chromatographic column separates methane passing through the internal gas;
s3 blowback: switching the multi-way sampling valve to be in a load state, starting a heating device of the pre-trap, releasing the adsorbed non-methane total hydrocarbons by a non-methane total hydrocarbon adsorbent arranged in the pre-trap, dividing carrier gas into two paths, enabling one path of carrier gas to enter the pre-trap through a first carrier gas inlet, and reversely blowing the released non-methane total hydrocarbons to a detector; the other path enters a chromatographic column through a second carrier gas inlet, and the separated methane is blown to a detector;
s4 detection: and detecting by a detector to obtain a detection result.
In a preferred embodiment, in the S3 blowback process, the multi-way injection valve is switched and simultaneously the gas compensation control valve is opened, so that the gas in the gas compensation source enters the first carrier gas channel.
In a preferred embodiment, the gas flow controller and the exhaust pump are closed during blow back.
The device and the method for directly detecting the content of the non-methane total hydrocarbons in the ambient air disclosed by the invention have the following beneficial effects:
(1) the non-methane total hydrocarbons are adsorbed by the pre-trap, so that the non-methane total hydrocarbons in the sample gas are separated in advance, the non-methane total hydrocarbons do not need to be separated by the chromatographic column, the separation efficiency and the detection precision are improved, and the content detection values of the non-methane total hydrocarbons and methane can be obtained at the same time;
(2) the trap pipe is heated by the heating device, so that the trap pipe is rapidly heated, the release speed of the non-methane total hydrocarbon is increased, the sample introduction bandwidth is narrowed, the chromatographic peak of the non-methane total hydrocarbon is fine and high, and the detection precision is improved;
(3) when the gas supplementing channel is adopted, the time for non-methane total hydrocarbon to enter the detector can be accelerated, the sample introduction bandwidth is further narrowed, and the detection precision is improved;
(4) low detection limit, high detection precision and high sensitivity.
Drawings
FIG. 1 is a schematic structural diagram of a non-methane content detection device provided by the invention in a load state;
FIG. 2 is a schematic structural diagram of a non-methane content detection device provided by the invention in a sampling state;
FIG. 3 is a schematic view of a pre-trap;
fig. 4 is a longitudinal cross-sectional view of the pre-trap.
Illustration of the drawings:
10. the gas-carrying device comprises a gas-carrying port, 11, a first gas resistor, 12, a second gas resistor, 20, a sample gas port, 21, a gas flow controller, 22, an exhaust pump, 3, a ten-way valve, 4, a pre-trap, 5, a quantitative ring, 6, a chromatographic column, 7, a detector, 40, a heating device, 41, a first trap pipe, 42, a second trap pipe, 43, a hot gas injector, 44, a hot gas source, 45, a condensing device, 46, a low-temperature gas source, 47, a low-temperature gas injector, 81, a supplementary control valve, 82 and a supplementary gas source.
Detailed Description
The invention provides a device and a method for detecting the content of non-methane total hydrocarbons in ambient air, and in order to make the purpose, technical scheme and effect of the invention clearer and clearer, the invention is further described in detail below by referring to the attached drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
Example 1
The apparatus for detecting the content of non-methane total hydrocarbons in ambient air, as shown in fig. 1 and fig. 2, includes a carrier gas port 10, a sample gas port 20, a gas flow controller 21, an exhaust pump 22, a ten-way valve 3, a pre-trap 4, a quantification ring 5, a chromatographic column 6, a first air resistor 11, a second air resistor 12, and a detector 7.
As shown in fig. 1 and fig. 2, interfaces of the ten-way valve 3 are respectively denoted by a0 to a9, interfaces a1 and a2, A3 and a4, A5 and A6, a7 and A8, and a9 and a0 of the ten-way valve 3 in the load state are connected, and when the ten-way valve 3 is switched to the sampling state, the interfaces a1 and a0, A3 and a2, A5 and a4, a7 and A6, and a9 and A8 are connected.
As shown in fig. 3, the pre-trap 4 includes a first trap pipe 41, a second trap pipe 42, and a heating device 40. Inside the first collection pipe 41, Tenax TA or Tenax GR adsorbent is placed for adsorbing high boiling point non-methane total hydrocarbons, and inside the second collection pipe 42, activated carbon adsorbent is placed for adsorbing low boiling point non-methane total hydrocarbons. The heating device may be a heating wire disposed on the outer surface of the first collecting pipe 41 and the second collecting pipe 42, or may be a hot air jet type heating device. As shown in fig. 3 and 4, the hot gas flow injection type heating apparatus includes a hot gas source 44 and a hot gas flow injector 43 connected to each other, and the injection port of the hot gas flow injector 43 is flat and faces the first and second collecting pipes 41 and 42. The hot air jet type heating device has high heating efficiency, and can quickly heat the first collecting pipe 41 and the second collecting pipe 42, so that the non-methane total hydrocarbon is quickly released in the back blowing process.
As shown in fig. 4, the pre-catcher 4 further includes a condensing device 45, and the condensing device 45 includes a low-temperature gas flow source 46 and a low-temperature gas flow ejector 47 connected to each other, and the ejection port of the low-temperature gas flow ejector 47 is flat and faces the first and second catching pipes 41 and 42.
As shown in fig. 1 and fig. 2, the carrier gas entering from the carrier gas port 10 is divided into two paths, one path is directly connected to the A3 interface, and the other path is connected to the second gas resistor 12 and then to the a6 interface, that is, the A3 interface is the first carrier gas inlet, and the a6 interface is the second carrier gas inlet. The sample gas port 20 is directly connected to the a1 interface, i.e., the a1 interface is the sample gas inlet. The A4 interface, the second collecting pipe 42, the first collecting pipe 41 and the A8 interface are connected in sequence; the A7 interface, the first air resistor 11 and the detector 7 are connected in sequence. The A5 interface, the chromatographic column 6 and the detector 7 are connected in sequence. The A2 interface, the quantitative ring 5 and the A9 interface are connected in sequence. The a0 interface, the gas flow controller 21, and the exhaust pump 22 are connected in this order.
An air supply pipe is connected between the port a4 and the second collection pipe 42, and the air supply pipe is connected to an air supply control valve 81 and an air supply source 82 in this order. During the blowback process, the make-up control valve 81 is opened, and the carrier gas in the make-up source 82 and the carrier gas entering through the first carrier gas inlet, i.e., the a3 interface, are brought together to the second collection pipe 42.
Example 2
The embodiment provides a method for detecting the content of non-methane total hydrocarbons, which comprises the following steps:
s1 sample injection:
the ten-way valve 3 is in a load state, as shown in fig. 1, one path of carrier gas passes through the A3 interface, the a4 interface, the second collecting pipe 42, the first collecting pipe 41, the A8 interface, the a7 interface, the first air resistor 11, and finally reaches the detector 7, and this channel is a first carrier gas channel. The other carrier gas passes through the second air lock 12, the A6 interface, the A5 interface, the chromatographic column 6 and finally reaches the detector 7, and the channel is a second carrier gas channel. After carrier gas in the first carrier gas channel passes through the pre-trap 4 and carrier gas in the second carrier gas channel passes through the chromatographic column 6, air in the pre-trap 4 and the chromatographic column 6 can be discharged, detection errors caused by air remaining in the pre-trap 4 and the chromatographic column 6 are avoided, and the improvement of the testing precision is facilitated. Meanwhile, the sample gas is finally discharged from the exhaust pump 22 through the a1 port, the a2 port, the dosing ring 5, the a9 port, the a0 port, and the gas flow controller 21, which is a sample gas passage. The quantitative ring 5 is filled with a sample gas, and the remaining sample gas is discharged by the exhaust pump 22 after passing through the gas flow controller 21.
S2 sampling:
the ten-way valve 3 is switched into the sampling state as shown in fig. 2. At this time, the carrier gas port 10 sequentially passes through an A3 port, an a2 port, the dosing ring 5, an a9 port, an A8 port, the first trap pipe 41, the second trap pipe 42, an a4 port, an a5 port, the chromatography column 6, and finally reaches the detector 7, and this passage is a third carrier gas passage. The sample gas in the quantitative ring 5 passes through the pre-trap 4 and then to the chromatographic column 6 under the action of the carrier gas. The carrier gas and the sample gas in the quantitative ring 5 pass through the first collecting pipe 41, the weak adsorbent such as Tenax TA and/or Tenax GR arranged in the first collecting pipe adsorbs the high-boiling point non-methane total hydrocarbons, then pass through the second collecting pipe 42, the strong adsorbent such as activated carbon adsorbent arranged in the second collecting pipe adsorbs the low-boiling point non-methane total hydrocarbons, the rest gas including the carrier gas, the methane and the oxygen in the sample gas and the like reach the chromatographic column 6, and the methane and the oxygen and the like are separated in the chromatographic column 6. Meanwhile, the other path of carrier gas sequentially passes through the second air resistor 12, the A6 interface, the A7 interface, the first air resistor 11 and the detector 7. The sample gas is discharged through the sample gas port 10, the a1 port, the a0 port, the gas flow controller 21, and the exhaust pump 22. The exhaust pump 22 and gas flow controller 21 may also be turned off at this stage to reduce the sample gas output.
S3 blowback:
the ten-way valve 3 is switched to a load state, and the heating device 40 is turned on to heat the first and second collecting pipes 41 and 42. As shown in fig. 1, the carrier gas enters the first carrier gas channel, passes through the second header 42, the first header 41, and the first air resistor 11 in this order, and then reaches the detector 7. Under the action of the heating device 40, the temperature of the first collecting pipe 41 and the second collecting pipe 42 is raised to a preset temperature, such as 120 ℃, and the adsorbents in the first collecting pipe 41 and the second collecting pipe 42 rapidly release non-methane total hydrocarbons adsorbed by the adsorbents and then enter the detector 7 under the action of the carrier gas. The other path of carrier gas enters a second carrier gas channel, passes through the chromatographic column 6, and blows methane and oxygen separated from the chromatographic column 6 to the detector 7.
S4 detection:
the tester 7 is started and detects to obtain a chromatogram comprising a non-methane total hydrocarbon chromatographic peak and a methane chromatographic peak.
Under the condition that the gas supplementing source 82 and the gas supplementing control valve 81 are arranged, in the back blowing process of S3, the gas supplementing control valve 81 can be opened to increase the flow rate of the carrier gas, so that the time interval of the non-methane total hydrocarbon entering the detector 7 is reduced, the sample introduction bandwidth is further narrowed, and the detection precision is improved. After completion of the detection at S4, the air supply control valve 81 is closed.
After the test is finished, if the next test needs to be performed in a short time, the condensing device 45 can be used for performing low-temperature air jet on the first condensation pipe 41 and the second condensation pipe 42, so that the first condensation pipe 41 and the second condensation pipe 42 can be cooled rapidly.
The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.
Claims (8)
1. A device for detecting the content of non-methane total hydrocarbons in ambient air, comprising: a multi-way sample injection valve, a carrier gas channel, a sample gas channel, a quantitative ring, a pre-trap, a chromatographic column, a gas flow controller and a detector;
the chromatographic column is a capillary column;
the pre-trap comprises a trapping pipe and a heating device, wherein the trapping pipe is internally provided with a non-methane total hydrocarbon adsorbent, and the heating device is arranged on the outer surface of the trapping pipe and used for heating the trapping pipe.
The multi-way sample injection valve comprises a first carrier gas inlet, a second carrier gas inlet and a sample gas inlet; the multi-way sampling valve has two working states: the device comprises a load state and a sampling state, and can be switched between the load state and the sampling state;
when the multi-way sampling valve is in a load state, one path of carrier gas sequentially passes through the first carrier gas inlet and the collecting pipe and then enters the detector to form a first carrier gas channel; the other path of carrier gas sequentially passes through the second carrier gas inlet and the chromatographic column and then reaches the detector to form a second carrier gas channel; the sample gas sequentially passes through the sample gas inlet, the quantitative ring and the gas flow controller to form a first sample gas channel;
when the multi-way sampling valve is in a sampling state, one path of carrier gas sequentially passes through the first carrier gas inlet, the quantitative ring, the collecting pipe and the chromatographic column and then reaches the detector to form a third carrier gas channel; the other path of carrier gas is connected with the second carrier gas inlet and then reaches the detector to form a fourth carrier gas channel; the sample gas port is sequentially connected with the sample gas inlet and the gas flow controller to form a second sample gas channel.
2. The detection device according to claim 1, wherein the collection tube comprises a first collection tube and a second collection tube which are connected with each other, and the multi-way sample injection valve is used for sequentially conveying the carrier gas to the first collection tube and the second collection tube after passing through the quantitative ring in a sampling state.
3. The detection apparatus according to claim 1, wherein the heating device is a hot air jet type heating device comprising a hot air source and a hot air jet connected to each other, the jet of the hot air jet being directed towards the trap pipe.
4. The detection apparatus of claim 3, wherein the pre-trap further comprises a condensing device comprising a source of cryogenic gas flow and a cryogenic gas flow ejector connected to each other, the cryogenic gas flow ejector having an orifice directed toward the trap tube.
5. The detection device of claim 1, further comprising a gas block, the gas block comprising a first gas block and a second gas block, the first gas block disposed on the first carrier gas channel between the pre-trap and the detector; the second air resistor is arranged on the second carrier gas channel and between the carrier gas source and the second carrier gas inlet.
6. The detection device as claimed in claim 5, further comprising an air replenishment passage including an air replenishment source connected between the first carrier gas inlet and the pre-trap through an air replenishment pipe, the air replenishment pipe being provided with an air replenishment control valve.
7. A method for detecting the content of non-methane total hydrocarbons in ambient air is characterized by comprising the following steps:
s1 sample injection: the multi-way sample injection valve is in a load state, the carrier gas is divided into two paths, one path sequentially passes through the first carrier gas inlet, the pre-trap and the detector, and the other path sequentially passes through the second carrier gas inlet, the chromatographic column and the detector; the sample gas sequentially passes through the sample gas inlet, the quantitative pipe and the gas flow controller;
s2 sampling: switching the multi-way sampling valve to be in a sampling state, wherein the carrier gas flows through a first carrier gas inlet, a quantitative ring, a pre-trap, a chromatographic column and a detector; the pre-trap adsorbs non-methane populations in the gas passing through the pre-trap, and the chromatographic column separates methane in the passing internal gas;
s3 blowback: switching the multi-way sampling valve to be in a load state, starting a heating device of the pre-trap, releasing the adsorbed non-methane total hydrocarbons by a non-methane total hydrocarbon adsorbent arranged in the pre-trap, dividing carrier gas into two paths, enabling one path of carrier gas to enter the pre-trap through a first carrier gas inlet, and reversely blowing the released non-methane total hydrocarbons to a detector; the other path enters a chromatographic column through a second carrier gas inlet, and the separated methane is blown to a detector;
s4 detection: and detecting by a detector to obtain a detection result.
8. The detection method according to claim 7, wherein in the S3 blowback process, the multi-way sample injection valve is switched, and simultaneously, an air supplement control valve is opened, so that the gas in an air supplement source enters the first carrier gas channel.
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| CN202010685981.3A CN111830155A (en) | 2020-07-16 | 2020-07-16 | Device and method for detecting content of non-methane total hydrocarbons in ambient air |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113155988A (en) * | 2020-12-31 | 2021-07-23 | 杭州谱育科技发展有限公司 | Non-methane total hydrocarbon detection system and method based on single valve |
| CN113624895A (en) * | 2021-07-31 | 2021-11-09 | 杭州谱育科技发展有限公司 | Direct measurement device and method for methane and non-methane total hydrocarbons |
| CN114324652A (en) * | 2021-12-29 | 2022-04-12 | 杭州谱育科技发展有限公司 | Gas detection device and method based on chromatographic technology |
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2020
- 2020-07-16 CN CN202010685981.3A patent/CN111830155A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113155988A (en) * | 2020-12-31 | 2021-07-23 | 杭州谱育科技发展有限公司 | Non-methane total hydrocarbon detection system and method based on single valve |
| CN113624895A (en) * | 2021-07-31 | 2021-11-09 | 杭州谱育科技发展有限公司 | Direct measurement device and method for methane and non-methane total hydrocarbons |
| CN114324652A (en) * | 2021-12-29 | 2022-04-12 | 杭州谱育科技发展有限公司 | Gas detection device and method based on chromatographic technology |
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