CN117147671B - Non-methane total hydrocarbon detection device and method based on dilution technology - Google Patents
Non-methane total hydrocarbon detection device and method based on dilution technology Download PDFInfo
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- CN117147671B CN117147671B CN202311415806.2A CN202311415806A CN117147671B CN 117147671 B CN117147671 B CN 117147671B CN 202311415806 A CN202311415806 A CN 202311415806A CN 117147671 B CN117147671 B CN 117147671B
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- 229930195733 hydrocarbon Natural products 0.000 title claims abstract description 55
- 239000004215 Carbon black (E152) Substances 0.000 title claims abstract description 53
- 150000002430 hydrocarbons Chemical class 0.000 title claims abstract description 46
- 239000012895 dilution Substances 0.000 title claims abstract description 37
- 238000010790 dilution Methods 0.000 title claims abstract description 37
- 238000001514 detection method Methods 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000005516 engineering process Methods 0.000 title claims abstract description 18
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 93
- 230000003197 catalytic effect Effects 0.000 claims abstract description 49
- 239000007789 gas Substances 0.000 claims description 121
- 239000001301 oxygen Substances 0.000 claims description 55
- 229910052760 oxygen Inorganic materials 0.000 claims description 55
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 54
- 238000004891 communication Methods 0.000 claims description 37
- 239000003054 catalyst Substances 0.000 claims description 32
- 238000005070 sampling Methods 0.000 claims description 15
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000011144 upstream manufacturing Methods 0.000 claims description 11
- 230000004913 activation Effects 0.000 claims description 9
- -1 methane hydrocarbon Chemical class 0.000 claims description 9
- 239000001294 propane Substances 0.000 claims description 7
- 238000002347 injection Methods 0.000 claims description 6
- 239000007924 injection Substances 0.000 claims description 6
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- 239000011324 bead Substances 0.000 claims description 4
- 238000002485 combustion reaction Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 15
- 239000003546 flue gas Substances 0.000 description 15
- 238000005259 measurement Methods 0.000 description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 238000012937 correction Methods 0.000 description 3
- 230000002035 prolonged effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000000567 combustion gas Substances 0.000 description 2
- 239000003085 diluting agent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000012855 volatile organic compound Substances 0.000 description 1
- 239000002912 waste gas Substances 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
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/626—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using heat to ionise a gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/38—Diluting, dispersing or mixing samples
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0011—Sample conditioning
- G01N33/0018—Sample conditioning by diluting a gas
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0031—General constructional details of gas analysers, e.g. portable test equipment concerning the detector comprising two or more sensors, e.g. a sensor array
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
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- General Engineering & Computer Science (AREA)
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Abstract
The invention provides a non-methane total hydrocarbon detection device and a method based on a dilution technology, wherein in the detection device, the input ends of a first pipeline and a second pipeline are communicated with a sample gas pipeline, a catalytic unit and a first detector are sequentially arranged on the first pipeline, and a second detector is arranged on the second pipeline; the first group of air resistors are arranged on the first pipeline, the second group of air resistors are arranged on the second pipeline, and the gas in the sample gas pipeline enters the first detector and the second detector respectively at the same flow rate; the output end of the third pipeline is communicated with the sample gas pipeline, the fourth pipeline is respectively communicated with the sample gas pipeline and the sixth pipeline and is provided with an emptying port, the input end of the fifth pipeline is communicated with the sample gas pipeline and is provided with an emptying port, and the sixth pipeline is communicated with the fifth pipeline; the flow controllers are respectively arranged on the third pipeline, the fourth pipeline and the sixth pipeline; the pressure sensors are respectively arranged on the sample gas pipeline, the third pipeline and the fifth pipeline. The invention has the advantages of accurate detection and the like.
Description
Technical Field
The invention relates to gas detection, in particular to a non-methane total hydrocarbon detection device and method based on dilution technology.
Background
At present, the determination of the non-methane total hydrocarbon by the catalytic method is mainly based on a hydrogen flame ionization detector, and the non-methane total hydrocarbon content in the sample gas can be obtained by measuring the total hydrocarbon content and the methane content in the sample gas and differentiating the total hydrocarbon content and the methane content. However, when the hydrogen flame ionization detector (i.e. the FID detector) is adopted to measure the total hydrocarbon concentration, the oxygen content influences the flame combustion state of the detector due to the synergistic effect of oxygen on the FID detector, so that the response sensitivity of the FID detector is influenced, and the measurement result is interfered, so that the oxygen interference has definite technical indexes in both instrument design and technical standards, and the oxygen interference index is required to be not more than +/-2% of full range according to the technical requirements of a fixed pollution source waste gas non-methane total hydrocarbon continuous monitoring system and the requirements of section 6.1.9 in the standard of a detection method HJ 1013-2018.
For the influence of oxygen interference on the accuracy of the measurement result of the FID detector, CN114397395A and CN112649549A respectively disclose a method for correcting the total hydrocarbon measurement concentration value of the gas to be measured by using a polynomial fitting oxygen interference correction model to obtain the corrected total hydrocarbon concentration value of the gas to be measured. CN115718148A discloses a method for performing oxygen compensation on a gas sample to be detected by setting a compensation gas circuit in a gas circuit at the front end of a nozzle inlet of an FID detector, so as to compensate the oxygen concentration of the gas sample to be detected to a target reference oxygen concentration.
The disadvantage of the above-mentioned patent method is that:
1. the oxygen concentration is required to be measured, the interference caused by the known oxygen concentration to the oxygen is corrected in real time, the correction effect of the oxygen concentration is dependent on the accurate measurement of the oxygen concentration, and once the oxygen measuring sensor fails or drifts, the correction effect of the oxygen interference is directly affected.
2. The catalyst is used in a high-concentration volatile organic compound environment, particularly in a low-oxygen environment, and can accelerate the catalyst to lose effectiveness, so that the catalytic efficiency of non-methane total hydrocarbon is reduced.
Disclosure of Invention
In order to solve the defects in the prior art scheme, the invention provides a non-methane total hydrocarbon detection device based on a dilution technology.
The invention aims at realizing the following technical scheme:
the non-methane total hydrocarbon detection device based on the dilution technology comprises a sample gas pipeline, a first pipeline and a second pipeline, wherein the input ends of the first pipeline and the second pipeline are communicated with the sample gas pipeline, the catalytic unit and the first detector are sequentially arranged on the first pipeline, and the second detector is arranged on the second pipeline; the non-methane total hydrocarbon detection device based on the dilution technology further comprises:
a first set of air resistors and a second set of air resistors, wherein the first set of air resistors are arranged on a first pipeline and are positioned at the upstream of a first detector, the second set of air resistors are arranged on a second pipeline and are positioned at the upstream of a second detector, and the gas in the sample gas pipeline enters the first detector and the second detector respectively at the same flow rate;
the output end of the third pipeline is communicated with the sample gas pipeline, the fourth pipeline is respectively communicated with the sample gas pipeline and the sixth pipeline and is provided with an emptying port, the input end of the fifth pipeline is communicated with the sample gas pipeline and is provided with an emptying port, and the sixth pipeline is communicated with the fifth pipeline;
the flow controllers are respectively arranged on the third pipeline, the fourth pipeline and the sixth pipeline;
and the pressure sensors are respectively arranged on the sample gas pipeline, the third pipeline and the fifth pipeline.
The invention also aims to provide a method for detecting the total non-methane hydrocarbon based on the dilution technology, which is realized by the following technical scheme:
the non-methane total hydrocarbon detection method based on the dilution technology comprises the following steps:
(S1) enabling propane under different oxygen background concentrations to enter a sample gas pipeline in a time-division mode, then enabling the propane to enter a first detector on a first pipeline and a second detector on a second pipeline at the same flow rate respectively, obtaining non-methane total hydrocarbon content under different oxygen background concentrations, and arranging a catalytic unit on the first pipeline at the upstream of the first detector;
(S2) judging whether the change rate of the total non-methane hydrocarbon content relative to the oxygen background concentration is smaller than a set value in the selected sample gas background concentration interval;
if so, the working parameters of the first detector and the second detector are saved;
if not, adjusting the working parameters of the first detector and the second detector, and returning to the step (S1);
(S3) the gas to be detected enters the sample gas pipeline, air enters the sample gas pipeline through a third pipeline, and the mixed gas enters the first detector and the second detector respectively at the same flow, wherein the first detector and the second detector work according to the stored working parameters;
(S4) adjusting the flow ratio of the air to the gas to be detected so that the oxygen concentration in the mixed gas is in the oxygen background concentration range;
(S5) outputting signals from the first detector and the second detector, thereby obtaining the total non-methane hydrocarbon content in the gas to be detected.
Compared with the prior art, the invention has the following beneficial effects:
1. the oxygen concentration does not need to be detected;
the optimal oxygen background concentration interval and the adjustment of working parameters are utilized, so that the interference caused by the change of the oxygen concentration is eliminated, the detection precision is improved, air is used as diluent gas, and the oxygen concentration is not required to be detected;
2. double-balanced double-detector detection is realized;
the first detector and the second detector work under the same working condition, even if the external environment changes, such as the sample injection pressure, the hydrogen pressure and the air pressure are controlled in imbalance caused by the change of the temperature, the air source pressure and the vibration environment, the consistency of the working conditions of the two paths of detectors can be ensured, the interference on NMHC measurement caused by the response difference of the detectors (such as FID) due to the change of the two paths of working conditions when the non-methane total hydrocarbon is calculated is avoided to the greatest extent, and meanwhile, the detection accuracy is improved without the measurement error caused by the difference of the response factors of methane and propane;
the second catalytic furnace is arranged on the second pipeline, and non-catalyst particles are arranged in the second pipeline, so that the resistance of gas passing through the catalytic unit is the same as that of gas passing through the second catalytic furnace, the passing time is the same, and double balance is better realized;
3. the bistable dilution ratio can be dynamically adjusted;
flow controllers are respectively arranged on the third pipeline, the fourth pipeline and the sixth pipeline, when the dilution ratio needs to be adjusted on site, the flow controllers on the third pipeline and the fourth pipeline can be adjusted to adjust the sampling pressure at the downstream of the sampling pump on the sampling gas pipeline, and meanwhile, the flow controllers on the sixth pipeline are used for adjusting the sampling pressure of the detector, so that the response characteristic and the oxygen interference curve of the detector are kept unchanged when the dilution ratio is changed; the dynamic range of the dilution ratio is wide, and the control precision of the dilution ratio is high; the dilution ratio is dynamically adjustable; the dilution ratio is not affected by the variation of the evacuation back pressure;
when the concentration of the sample gas on site is too high or the service life of the catalyst is reduced too quickly, the catalyst can be realized by adjusting the dilution ratio, and if the dilution ratio is set to be 10 times, the service life of the catalyst is prolonged by at least more than 10 times;
4. realizing zero point real-time dynamic compensation and dynamic activation of the catalyst;
adjusting the pressure of the sample gas pipeline downstream of the sampling pump, maintaining the pressure on the third pipeline and the inlet pressure of the first pipeline unchanged, so that the pressure of the pump downstream is smaller than the inlet pressure, and enabling the pressure of the sample gas pipeline downstream of the sampling pump to be smaller than the inlet pressure:
in the opposite CH 4 In the zero setting calibration of NMHC and THC, only air enters the detector, and the environment change pair CH can be compensated in real time 4 The NMHC and THC measurement influence, so that the requirement of the instrument on zero gas purity is obviously reduced, and the offset risk of the zero gas unit failure instrument is reduced;
in the catalyst activation, only air enters the catalytic unit, so that the service life of the catalyst is greatly prolonged, the exposure time of the catalyst under toxic and harmful gases is reduced, and the service life of the catalyst is prolonged.
Drawings
The present disclosure will become more readily understood with reference to the accompanying drawings. As will be readily appreciated by those skilled in the art: the drawings are only for illustrating the technical scheme of the present invention and are not intended to limit the scope of the present invention. In the figure:
FIG. 1 is a schematic diagram of a non-methane total hydrocarbon detection device based on a dilution technique in accordance with an embodiment of the invention;
FIG. 2 is a graph of non-methane total hydrocarbon content versus oxygen background concentration in accordance with an embodiment of the present invention;
FIG. 3 is a graph of non-methane total hydrocarbon content versus oxygen background concentration in accordance with an embodiment of the present invention.
Detailed Description
Figures 1-3 and the following description depict alternative embodiments of the invention to teach those skilled in the art how to make and reproduce the invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations or alternatives derived from these embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Thus, the invention is not limited to the following alternative embodiments, but only by the claims and their equivalents.
Example 1:
in the non-methane total hydrocarbon detection device based on the dilution technology according to the embodiment of the invention, as shown in fig. 1, the non-methane total hydrocarbon detection device based on the dilution technology includes:
the sample gas pipeline 10, the first pipeline 11 and the second pipeline 12, wherein the input ends of the first pipeline 11 and the second pipeline 12 are communicated with the sample gas pipeline 10, the catalytic unit 71 and the first detector 81 are sequentially arranged on the first pipeline 11, and the second detector 82 is arranged on the second pipeline 12;
a first group of air resistors and a second group of air resistors, wherein the first group of air resistors are arranged on the first pipeline 11, the second group of air resistors are arranged on the second pipeline 12, and the gas in the sample gas pipeline 10 respectively enters the first detector 81 and the second detector 82 at the same flow rate;
a third pipeline 13, a fourth pipeline 14, a fifth pipeline 15 and a sixth pipeline 16, wherein the output end of the third pipeline 13 is communicated with the sample gas pipeline 10, the fourth pipeline 14 is respectively communicated with the sample gas pipeline 10 and the sixth pipeline 16, and is provided with an emptying port, the input end of the fifth pipeline 15 is communicated with the sample gas pipeline 10, and is provided with an emptying port, and the sixth pipeline 16 is communicated with the fifth pipeline 15;
flow controllers provided on the third pipe 13, the fourth pipe 14, and the sixth pipe 16, respectively;
pressure sensors are provided on the sample gas channel 10, the third channel 13 and the fifth channel 15, respectively.
In order to regulate the pressure on the sample gas channel 10, further, a first connection point 51 between the fourth channel 14 and the sample gas channel 10 is located upstream of a second connection point 52 between the third channel 13 and the sample gas channel 10, and the first pressure sensor 31 is located at the first connection point 51;
the third connection 53 between the sixth conduit 16 and the fourth conduit 14 is upstream of the fourth connection 54 between the fourth conduit and the sample gas conduit 10.
In order to make the gas flow rates into the first detector 81 and the second detector 82 the same, further, the first set of air-lock and the air-lock generated by the catalytic unit 71 are the same as the air-lock generated by the second set of air-lock.
In order to make the flow rates on the first pipe 11 and the second pipe 12 the same, further, the catalytic unit 71 comprises a first catalytic furnace and a catalyst, the second group of air resistors comprises a second air resistor 62 and a second catalytic furnace 72, and the second catalytic furnace 72 is filled with non-catalyst particles, and the diameter and the number of the non-catalyst particles are the same as those of the catalyst.
The non-methane total hydrocarbon detection method based on the dilution technology provided by the embodiment of the invention comprises the following steps:
(S1) propane at different oxygen background concentrations enters the sample gas pipeline 10 in time, then enters the first detector 81 on the first pipeline 11 and the second detector 82 on the second pipeline 12 at the same flow rate respectively to obtain non-methane total hydrocarbon contents at different oxygen background concentrations, and a catalytic unit 71 is arranged on the first pipeline 11 and upstream of the first detector 81;
(S2) judging whether the change rate of the total non-methane hydrocarbon content relative to the oxygen background concentration is smaller than a set value in the selected oxygen background concentration interval;
if so, preserving the operating parameters of the first and second detectors 81, 82;
if not, adjusting the operation parameters of the first detector 81 and the second detector 82, and returning to step (S1);
(S3) the gas to be measured enters the sample gas pipeline 10, air enters the sample gas pipeline 10 through the third pipeline 13, and the mixed gas enters the first detector 81 and the second detector 82 respectively at the same flow rate, and the first detector 81 and the second detector 82 work according to the stored working parameters;
(S4) adjusting the flow ratio of the air to the gas to be detected so that the oxygen concentration in the mixed gas is in the oxygen background concentration range;
(S5) the first detector 81 and the second detector 82 output signals to obtain the non-methane total hydrocarbon content in the gas to be measured.
For zeroing and catalyst activation, further, the specific modes of zeroing and catalyst activation are:
the pressure on the sample line 10 downstream of the sampling pump 41 is regulated, maintaining the pressure on the third line 13 and the inlet pressure of the first line 11 unchanged, so that the pressure downstream of the sampling pump 41 is less than the inlet pressure, so that in the zeroing only air enters the first detector 81 and the second detector 82, and in the catalyst activation only air enters the catalytic unit.
In order to make the gas flow rate and time of the gas entering the first detector 81 and the second detector 82 be the same, further, on the first pipeline 11, the first gas resistor 61, the catalytic unit 71 and the first detector 81 are sequentially arranged, the catalytic unit 71 comprises a first catalytic furnace and a catalyst, on the second pipeline 12, the second gas resistor 62, the second catalytic furnace 72 and the second detector 82 are sequentially arranged, non-catalyst beads are arranged in the second catalytic furnace 72, the first gas resistor 61 and the second gas resistor 62 are the same, the gas resistors generated by the catalytic unit 71 and the second catalytic furnace 72 are the same, and the gas passing time is the same.
In order to dynamically adjust the dilution ratio, further, driving gas enters the fourth pipeline 14, part of the driving gas is mixed with the gas to be tested and then is exhausted, and part of the driving gas enters the fifth pipeline 15 through the sixth pipeline 16 and is mixed with the diluted gas to be tested and then is exhausted; the fourth pipeline 14 and the fifth pipeline 15 are respectively communicated with the sample gas pipeline 10.
Example 2:
application example of the non-methane total hydrocarbon detection device and method based on dilution technique in flue gas detection according to embodiment 1 of the present invention.
In this application example, as shown in fig. 1, a second flow controller 22 (EPC) and a fourth air resistor 64 are provided in this order on the third pipe 13, and the second pressure sensor 32 detects the pressure of the gas passing through the second flow controller 22. The sampling pump 41, the first communication point 51, the fifth air resistor 65, the second communication point 52 and the fifth communication point 55 are sequentially arranged on the sampling pipeline 10, the first pressure sensor 31 is arranged at the first communication point 51, the third pipeline 13 is communicated with the second communication point 52, and the first pipeline 11, the second pipeline 12 and the fifth pipeline 15 are all communicated with the fifth communication point 55. The fifth pipe 15 is provided with a sixth communication point 56 and a third air resistor 63 in sequence, and is provided with an evacuation port, and the third pressure sensor 33 is arranged at the sixth communication point 56.
The first pipe 11 is provided with a first air resistor 61, a seventh communication point 57, a catalytic unit 71 and a first detector 81 in sequence, the first detector 81 adopts FID, air is used as fuel gas, and the first detector 81 is communicated. The second pipe 12 is provided with a second air resistor 62, an eighth communication point 58, a second catalytic furnace 72 and a second detector 82 in sequence, the second detector 82 adopts FID, air is used as fuel gas, and the second detector 82 is communicated. The hydrogen gas as combustion gas enters the sixth communication point 56 and the seventh communication point 57 at the same flow rate. The first air resistor 61 and the second air resistor 62 are identical. The catalytic unit 71 includes a first catalytic furnace and a catalyst, the catalyst being spherical and filled in the first catalytic furnace; the second catalytic furnace 72 is identical to the first catalytic furnace, and glass beads or stainless steel beads are filled in the second catalytic furnace 72, and the diameter and the number are identical to those of the catalysts, so that when the gas passes through the first catalytic furnace and the second catalytic furnace respectively, the gas resistance is identical, and the passing time is also identical. Based on this, when the gas in the sample gas pipe 10 enters the first pipe 11 and the second pipe 12, the flow rate and the required time are the same, and the gas flow rate and the gas entry time through the first detector 81 and the second detector 82 are the same.
The fourth pipeline 14 is sequentially provided with a third communication point 53, a first flow controller 21 (EPC), a fourth communication point 54 and a sixth air resistor 66, and the tail end is an emptying port; the fourth communication point 54 communicates with the first communication point 51, the third communication point 53 communicates with a sixth communication point 56 through the sixth pipe 16, and the third flow controller 23 (EPC) is provided on the sixth pipe 16.
The method for detecting the non-methane total hydrocarbon based on the dilution technology, namely the working method of the device for detecting the non-methane total hydrocarbon of the embodiment, comprises the following steps:
(S1) the propane standard gas under different oxygen background concentrations (0-21%) enters the sample gas pipeline 10 in a time-division manner, and then enters the first detector 81 on the first pipeline 11 and the second detector 82 on the second pipeline 12 at the same flow rate respectively, so that the corresponding relation between the non-methane total hydrocarbon content and the oxygen background concentration is obtained, and as shown in fig. 2, the fluctuation of the non-methane total hydrocarbon content is large;
in this embodiment, the working parameters of the first detector 81 and the second detector 82 are: the sample injection flow is 20mL/min, the combustion gas (adopting hydrogen) flow is 20mL/min, and the combustion-supporting gas (adopting air) flow is 200mL/min.
(S2) in the selected oxygen background concentration interval, the oxygen background concentration interval of the embodiment is 10.5% -21%, and whether the change rate of the total non-methane hydrocarbon content relative to the oxygen background concentration is smaller than a set value or not is judged, wherein the set value of the embodiment is 2%; the smaller the set value is, the smaller the influence of the oxygen background concentration is after the total non-methane hydrocarbon content is, and the higher the subsequent detection precision is;
if so, the operating parameters of the first detector 81 and the second detector 82 are saved: the sample injection flow is 10mL/min, the combustion air flow is 30mL/min, the combustion air flow is 300mL/min, and the corresponding relation between the total non-methane hydrocarbon content and the oxygen background concentration is shown in figure 3;
if not, adjusting the operation parameters of the first detector 81 and the second detector 82, and returning to step (S1);
(S3) flue gas enters the sample gas pipeline 10, air enters the sample gas pipeline 10 through the third pipeline 13, part of the flue gas enters the fourth pipeline 14 through the first communication point 51 and the fourth communication point 54, then the flue gas is emptied, the rest flue gas and the air are converged at the second communication point 52, the (diluted flue gas) mixed gas enters the first detector 81 and the second detector 82 respectively at the same flow rate, and simultaneously enters the fifth pipeline 15, and the first detector 81 and the second detector 82 work according to the stored working parameters;
the driving gas, such as nitrogen, enters the fourth pipeline 14, part of the driving gas sequentially enters the sixth pipeline 16 and the fifth pipeline 15 from the third communication point 53, the diluted mixed gas entering from the fifth communication point 55 is mixed for evacuation, and part of the driving gas mixes the flue gas entering from the fourth communication point 54 and is then evacuated;
(S4) adjusting the ratio of the flows of the air and the flue gas so that the oxygen concentration in the flue gas and air mixture is in the background concentration range; at this time, the first detector 81 and the second detector 82 still operate according to the saved operation parameters;
in the embodiment, the oxygen concentration in the air is 21%, and the oxygen content in the flue gas is unknown but is 0-21%; in order to make the oxygen concentration in the air and flue gas mixture be in the background concentration range, the ratio of the air flow to the flue gas flow is not less than 1, and in this embodiment, 2 is taken;
the sample pressure and the dilution gas pressure downstream of the sampling pump 41 are adjusted by adjusting the first flow controller 21 and the second flow controller 22, while the third flow controller 23 is adjusted so that the sample pressure (i.e., the output value of the third pressure sensor 33) is kept constant, thereby ensuring that the response characteristics of the first detector 81 and the second detector 82 and the oxygen disturbance curve remain constant while the ratio of the flows is changed.
(S5) the first detector 81 and the second detector 82 output signals to obtain the non-methane total hydrocarbon content in the flue gas.
The specific modes of zeroing and catalyst activation are as follows:
the pressure downstream of the sampling pump 41 on the sampling pipe 10 is regulated, maintaining the pressure on the third pipe 13 and the intake pressure of the first pipe 11 unchanged, so that the pressure downstream of the sampling pump 41 is smaller than the intake pressure, so that:
in zeroing, the sample gas channel 10 is closed such that only air enters the first channel 11, the second channel 12, the first detector 81 and the second detector 82;
during catalyst activation, the sample gas line 10 is closed and only air enters the catalytic unit 71.
Example 3:
the application example of the non-methane total hydrocarbon detection device and method based on the dilution technique according to embodiment 1 of the present invention in flue gas detection is different from embodiment 2 in that:
1. on the second pipe 12, a gas lock is used instead of the second catalytic furnace.
2. The oxygen background concentration interval is 14% -21%, correspondingly, in the detection method, the ratio of the flow rate of air serving as diluent gas to the flow rate of flue gas is not less than 2, for example, 10 is taken.
Claims (8)
1. The non-methane total hydrocarbon detection method based on the dilution technology comprises the following steps:
(S1) enabling propane under different oxygen background concentrations to enter a sample gas pipeline in a time-division mode, then enabling the propane to enter a first detector on a first pipeline and a second detector on a second pipeline at the same flow rate respectively, obtaining non-methane total hydrocarbon content under different oxygen background concentrations, and arranging a catalytic unit on the first pipeline at the upstream of the first detector;
(S2) judging whether the change rate of the total non-methane hydrocarbon content relative to the oxygen background concentration is smaller than a set value in the selected oxygen background concentration interval;
if so, the working parameters of the first detector and the second detector are saved;
if not, adjusting the working parameters of the first detector and the second detector, and returning to the step (S1);
the working parameters comprise sample injection flow, combustion air flow and combustion-supporting air flow;
(S3) the gas to be measured enters the sample gas pipeline, air enters the sample gas pipeline through a third pipeline, part of the gas to be measured enters a fourth pipeline through a first communication point and a fourth communication point, then the gas to be measured is emptied, and the rest of the gas to be measured and the air are converged at a second communication point; the mixed gas enters the first detector and the second detector respectively at the same flow, and the first detector and the second detector work according to the stored working parameters; the second flow controller is arranged on the third pipeline;
the driving gas enters a fourth pipeline, part of the driving gas sequentially enters a sixth pipeline and a fifth pipeline from a third communication point, the diluted mixed gas entering from the fifth communication point is mixed for emptying, and part of the driving gas is mixed with the gas to be detected entering from the fourth communication point and then is emptied; the first flow controller is arranged between the third communication point and the fourth communication point; the first pipeline, the second pipeline and the fifth pipeline are all communicated with a fifth communication point on the sample gas pipeline, and the third flow controller is arranged on the sixth pipeline;
(S4) adjusting the flow ratio of the air to the gas to be detected so that the oxygen concentration in the gas to be detected and the air mixture is in the oxygen background concentration range;
the flow ratio is adjusted by the following steps: the sample injection pressure and the dilution air pressure at the downstream of the sampling pump are regulated by regulating the first flow controller and the second flow controller, and the third flow controller is regulated to keep the sample injection pressure unchanged, so that when the flow ratio is changed, the response characteristics of the first detector and the second detector and the oxygen interference curve are kept unchanged;
(S5) outputting signals from the first detector and the second detector, thereby obtaining the total non-methane hydrocarbon content in the gas to be detected.
2. The method for detecting non-methane total hydrocarbons based on dilution techniques according to claim 1, wherein: the non-methane total hydrocarbon detection method also comprises zeroing and catalyst activation, and specifically comprises the following steps:
the pressure downstream of the pump on the sample gas line is regulated, maintaining the pressure on the third line and the inlet pressure of the first line unchanged, such that the pressure downstream of the pump is less than the inlet pressure, such that in the zeroing only air enters the detector and in the catalyst activation only air enters the catalytic unit.
3. The method for detecting non-methane total hydrocarbons based on dilution techniques according to claim 1, wherein: the first air resistor, the catalytic unit and the first detector are sequentially arranged on the first pipeline, and the catalytic unit comprises a first catalytic furnace and a catalyst; on the second pipeline, a second air resistance, a second catalytic furnace and a second detector are sequentially arranged, non-catalyst beads are arranged in the second catalytic furnace, the first air resistance is the same as the second air resistance, and the air resistance generated when gas passes through the catalytic unit and the second catalytic furnace is the same.
4. The non-methane total hydrocarbon detection device based on the dilution technology for implementing the non-methane total hydrocarbon detection method according to claim 1 comprises a sample gas pipeline, a first pipeline and a second pipeline, wherein the input ends of the first pipeline and the second pipeline are communicated with the sample gas pipeline, the catalytic unit and the first detector are sequentially arranged on the first pipeline, and the second detector is arranged on the second pipeline; the method is characterized in that: the non-methane total hydrocarbon detection device based on the dilution technology further comprises:
a first set of air resistors and a second set of air resistors, wherein the first set of air resistors are arranged on a first pipeline and are positioned at the upstream of a first detector, the second set of air resistors are arranged on a second pipeline and are positioned at the upstream of a second detector, and the gas in the sample gas pipeline enters the first detector and the second detector respectively at the same flow rate;
the input end of the fifth pipeline is communicated with the sample gas pipeline and is provided with an emptying port, and the sixth pipeline is communicated with the fifth pipeline;
and the pressure sensors are respectively arranged on the sample gas pipeline, the third pipeline and the fifth pipeline.
5. The non-methane total hydrocarbon detection device based on the dilution technique according to claim 4, wherein: the first communication point between the fourth pipeline and the sample gas pipeline is located upstream of the second communication point between the third pipeline and the sample gas pipeline, and the first pressure sensor is located between the first communication point and the second communication point.
6. The non-methane total hydrocarbon detection apparatus based on dilution technique according to claim 5, wherein: the third connection point between the sixth conduit and the fourth conduit is upstream of the fourth connection point between the fourth conduit and the sample gas conduit.
7. The non-methane total hydrocarbon detection apparatus based on dilution technology according to claim 6, wherein: the air resistance generated by the first group of air resistances and the catalytic unit is the same as the air resistance generated by the second group of air resistances.
8. The non-methane total hydrocarbon detection apparatus based on dilution technology according to claim 7, wherein: the second group of air resistances comprises air resistances and a second catalytic furnace, non-catalyst particles are filled in the second catalytic furnace, and the diameters and the numbers of the non-catalyst particles are the same as those of the catalyst.
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