CN109682777B - System for detecting trace methane content in ultra-high purity gas based on cavity ring-down spectroscopy - Google Patents
System for detecting trace methane content in ultra-high purity gas based on cavity ring-down spectroscopy Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 238000000180 cavity ring-down spectroscopy Methods 0.000 title claims abstract description 20
- 230000003287 optical effect Effects 0.000 claims abstract description 119
- 238000005259 measurement Methods 0.000 claims abstract description 34
- 238000001514 detection method Methods 0.000 claims abstract description 32
- 239000007789 gas Substances 0.000 claims description 36
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 10
- 238000012795 verification Methods 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 description 9
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- 238000011010 flushing procedure Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 1
- 229910005542 GaSb Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- QGJOPFRUJISHPQ-NJFSPNSNSA-N carbon disulfide-14c Chemical compound S=[14C]=S QGJOPFRUJISHPQ-NJFSPNSNSA-N 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- CGKPGVZMSKVVOF-UHFFFAOYSA-N chloro(nitro)methane Chemical compound [O-][N+](=O)CCl CGKPGVZMSKVVOF-UHFFFAOYSA-N 0.000 description 1
- 229960001701 chloroform Drugs 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method 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
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- Analytical Chemistry (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Optics & Photonics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A system for detecting trace methane content in ultra-high purity gas based on an optical cavity ring-down spectroscopy technology comprises a DBF laser, an optical modulator, a first convex mirror, a small hole and a second convex mirror which are sequentially arranged on an optical axis; the system is characterized by further comprising two first rectangular prisms and two second rectangular prisms, wherein the first rectangular prisms and the second rectangular prisms are arranged at the rear end of the second convex lens, the rear end of each first rectangular prism is further provided with a first filter plate, a first optical cavity and a first detection device, the rear end of each second rectangular prism is further provided with a second filter plate, the second optical cavity and the second detection device are respectively connected with a data acquisition processor, the system is simple in structure, and the measurement accuracy is high.
Description
Technical Field
The invention relates to the field of measurement, in particular to a system for detecting trace methane content in ultra-high purity gas based on an optical cavity ring-down spectroscopy technology.
Background
Methane, chemical formula CH 4 Is the simplest hydrocarbon, consisting of one carbon and four hydrogen atoms hybridized by sp3, and having a regular tetrahedron structureIn the structure, the key lengths of the four keys are identical and the key angles are equal. Methane is a colorless odorless gas under standard conditions. Some of the biogas generated when organic matter is decomposed under anoxic conditions is in fact methane.
Methane is widely distributed in nature, is the simplest organic matter, commonly called gas, is the hydrocarbon with the smallest carbon content (the largest hydrogen content), and is also the main component of natural gas, biogas, oilfield gas and coal mine tunnel gas. Methane is mainly used as fuel, such as natural gas and coal gas, and is widely used in civil and industrial applications; as chemical raw materials, the catalyst can be used for producing acetylene, hydrogen, synthetic ammonia, carbon black, nitrochloromethane, carbon disulfide, chloromethane, dichloromethane, trichloromethane, carbon tetrachloride, hydrocyanic acid and the like.
High-precision trace gas detection is widely applied to various industries, bruce et al reveal star formation by detecting CO concentration, and just et al detect CO 2 The change of vegetation emissivity along with the change law of factors such as seasons and the like is explained by Chen Xiao detecting CO and CH 4 And determining the working state of the oil immersed transformer by the trace gas. In recent years, scholars have made a great deal of research on the aspects of gas monitoring modes, platform and instrument performances and the like for improving the detection precision of trace gas, wang and the like design a novel gas measurement platform based on a back Programming Logic Controller (PLC) so that the detection of the trace gas is not influenced by temperature and air pressure, and the detection precision is improved by three orders of magnitude; joel et al analyzed the influence of each performance parameter of the mid-infrared laser gas detection system on gas accuracy in detail; ventrudo et al have experimentally found that a GaSb-based Distributed Feedback (DFB) light source temperature higher or lower than ambient temperature is beneficial to improving the accuracy of trace gas detection, but there are few reports on how to treat the intensity signal after gas absorption to reduce the impact of interference factors on the accuracy of gas detection.
The existing measuring devices are complex, the light path of the existing measuring devices is often changed through the transmitting mirror, the existing measuring devices are easy to be disturbed, the precision is not high, and the existing measuring devices are large in size due to the arrangement mode.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a system for detecting the trace methane content in ultra-high purity gas based on an optical cavity ring-down spectroscopy technology, which has the advantages of simple structure and high measurement accuracy.
The invention provides a system for detecting trace methane content in ultra-high purity gas based on an optical cavity ring-down spectroscopy technology, which comprises a DBF laser, an optical modulator, a first convex mirror, a small hole and a second convex mirror, wherein the DBF laser, the optical modulator, the first convex mirror, the small hole and the second convex mirror are sequentially arranged on an optical axis;
the two rectangular prisms are respectively arranged on reflection curves of the laser emission direction of the DBF laser and the detection directions of the objects of the two target optical cavities, and the laser beams passing through the second convex mirror are respectively reflected in the first rectangular prism and the second rectangular prism for multiple times and then emitted in the detection directions of the objects of the two target optical cavities;
the rear end of the first rectangular prism is further provided with a first filter, a first optical cavity and a first detection device in sequence, the rear end of the second rectangular prism is further provided with a second filter, the second optical cavity and the second detection device are connected with a data acquisition processor respectively.
Preferably, the first and second heaters are respectively and correspondingly arranged on the two sides of the inner bottoms of the first and second optical cavities, and are respectively connected with the temperature controller which is also connected with the data acquisition processor.
Preferably, the inner bottoms of the first optical cavity and the second optical cavity are respectively provided with a heating layer, and the first heater and the second heater are arranged in the heating layers.
Preferably, one side of the inner top parts of the first optical cavity and the second optical cavity is respectively and correspondingly provided with a temperature sensing unit, and the temperature sensing units are respectively connected with a temperature detector.
Preferably, the first and second heaters are specifically heating wires or bohr patches.
The invention also provides a measuring method of the system for detecting the trace methane content in the ultra-high purity gas based on the cavity ring-down spectroscopy technology, which sequentially comprises the following steps:
(1) Under stable ambient temperature, respectively filling calibration gas into the first optical cavity and the second optical cavity, controlling the DBF laser to emit laser beams with specific wavelengths, and sequentially enabling the laser beams to enter the first convex lens, the small hole and the second convex lens after modulation of the optical modulator;
(2) The laser beam passing through the second convex mirror respectively enters the first rectangular prism and the second rectangular prism, is divided into two paths, passes through the first filter plate and the second filter plate and respectively enters the first optical cavity and the second optical cavity;
(3) The light beams after the first and second cavity ring-down are detected by the first and second detection devices and then sent to a data acquisition processor, and the measurement is carried out by utilizing the cavity ring-down spectroscopy;
(4) Comparing the two paths of measurement results, if the difference value is within the threshold range, entering the next step, otherwise, adjusting the system to ensure that the difference value of the two paths of measurement results meets the threshold range, and returning to the step (1);
(5) Starting measurement, respectively flushing target gas into the first optical cavity and the second optical cavity, respectively controlling the corresponding first heater and the corresponding second heater in the first optical cavity and the second optical cavity to start heating, simultaneously controlling the corresponding temperature sensing unit to start measurement according to a certain period, and entering the next step when the temperatures in the first optical cavity and the second optical cavity are stabilized within a preset temperature range;
(6) The DBF laser is controlled to emit laser beams with specific wavelength, the laser beams enter the optical modulator to be modulated, then the first convex lens, the small hole and the second convex lens are sequentially arranged, then the laser beams correspondingly enter the first rectangular prism and the second rectangular prism, respectively enter the first optical cavity and the second optical cavity after passing through the first filter and the second filter, and after being detected by the first detection device and the second detection device, the laser beams are sent to the data acquisition processor to be measured by utilizing the optical cavity ring-down spectroscopy technology.
Preferably, step (6) further comprises a temperature compensation verification step: the method comprises the steps of keeping target gases respectively flushed in two paths of first and second optical cavities, respectively controlling corresponding first and second heaters in the first and second optical cavities to start heating, and simultaneously controlling corresponding temperature sensing units to start measuring according to a certain period, so that the temperatures in the first and second optical cavities reach another temperature range different from a preset temperature range; and (3) returning to the step (6) when the temperatures in the first optical cavity and the second optical cavity are stable within another preset temperature range, calculating the influence relation of the temperature change on the measurement result according to a theoretical calculation mode, and verifying whether the precision of the system meets the requirement.
The system for detecting the trace methane content in the ultra-high purity gas based on the cavity ring-down spectroscopy technology can realize the following steps:
1) The structure is compact, and the measurement accuracy is high;
2) The heating is balanced, and the measurement accuracy is improved;
3) The rectangular prism replaces the reflector, the structure is simpler, the light path is more stable, and the measurement accuracy is higher.
Drawings
FIG. 1 is a schematic diagram of a system for detecting trace methane content in ultra-high purity gas based on cavity ring-down spectroscopy
In the figure: 1-DBF laser, 2-optical modulator, 3-first convex lens, 4-aperture, 5-second convex lens, 6-first rectangular prism, 7-first filter, 8-first optical cavity, 9-second rectangular prism, 10-second filter, 11-second optical cavity, 12-temperature sensor, 13-heater, 14-thermoscope, 15-temperature controller, 16-first detecting device, 17-second detecting device, 18-data acquisition processor.
Detailed Description
The following detailed description of the invention is provided for the purpose of further illustrating the invention and should not be construed as limiting the scope of the invention, as numerous insubstantial modifications and adaptations of the invention as described above will be apparent to those skilled in the art and are intended to be within the scope of the invention.
The invention provides a system for detecting trace methane content in ultra-high purity gas based on an optical cavity ring-down spectroscopy technology, which is shown in a figure 1, and comprises a DBF laser 1, an optical modulator 2, a first convex mirror 3, a small hole 4 and a second convex mirror 5 which are sequentially arranged on an optical axis, wherein after the DBF laser 1 emits laser with specific wavelength, the specific wavelength emitted by the DBF laser can be selected and regulated according to measurement requirements, output laser enters the optical modulator 2, the optical modulator 2 modulates the laser to meet emission requirements, and meanwhile, when the laser beam intensity reaches a certain threshold value, the laser beam is cut off, so that the laser beam can not be emitted any more.
The laser beam modulated by the optical modulator 2 enters the first convex mirror 3, the small hole 4 and the second convex mirror 5 respectively. The laser beam modulated by the optical modulator 2 is converged by the first convex mirror 3 and then passes through the small hole 4, wherein stray light can be effectively removed by the arrangement of the small hole 4, and noise is reduced. The light beam passing through the small hole 4 is changed into parallel light after passing through the second convex mirror 5.
The system for detecting the trace methane content in the ultra-high purity gas based on the cavity ring-down spectroscopy further comprises two first rectangular prisms 6 and two second rectangular prisms 9 which are arranged at the rear end of the second convex lens 5, wherein the two rectangular prisms are arranged up and down in the optical axis direction. The laser emitting direction of the DBF laser 1 is parallel to the detection directions of the objects of the two target optical cavities 8,11, and the two rectangular prisms are respectively arranged on reflection curves of the laser emitting direction of the DBF laser 1 and the detection directions of the objects of the two target optical cavities 8,11, and after the laser beams passing through the second convex mirror 5 pass through multiple reflections in the first rectangular prism 6 and the second rectangular prism 9 respectively, the laser beams are emitted to the detection directions of the objects of the two target optical cavities 8,11 in an emitting mode.
The rear end of the first rectangular prism 6 is further provided with a first filter 7, a first optical cavity 8, a first detection device 16 and the same arrangement mode, and the rear end of the second rectangular prism 9 is further provided with a second filter 10, a second optical cavity 11 and a second detection device 17. The first detecting device 16 and the second detecting device 17 are respectively connected with a data acquisition processor 18.
As shown in figure 1, during testing, the influence of temperature on the system is large, so that the invention designs a temperature control system for the target optical cavities 8 and 11, and accurate control of the temperature can ensure the accuracy of measurement data. Specifically, the first and second heaters 13, such as heating wires or bohr patches, are respectively and correspondingly arranged at two sides of the inner bottoms of the first and second optical cavities 8 and 11, and when the internal temperature of the target optical cavities 8 and 11 exceeds the measurement temperature range, the temperature can be changed by controlling the heaters, so that the requirement of measuring the temperature is met, the measurement precision is finally ensured, and compared with the prior art, the measurement precision is higher. The first heater 13 and the second heater 13 are respectively connected with a temperature controller 15, and the temperature controller 15 is also connected with a data acquisition processor 18. In order to ensure the uniformity and stability of heating, the inner bottoms of the target optical cavities 8,11 are provided with heating layers, and the first heater 13 and the second heater 13 are arranged in the heating layers, so that the heating is balanced, and the measurement accuracy is improved.
The temperature sensing units 12 are correspondingly arranged on one side of the inner top parts of the target optical cavities 8 and 11 respectively, the temperature sensing units 12 are connected with the thermometers 14 respectively, and the temperatures in the target optical cavities 8 and 11 are measured respectively in real time through the corresponding temperature sensing units 12, so that the temperatures in the cavities can be mastered in real time, and the measurement is ensured to be carried out at the stable temperature which accords with the measurement standard through the temperature control in the cavities.
The invention also provides a measuring method of the system for detecting the trace methane content in the ultra-high purity gas based on the cavity ring-down spectroscopy technology, which specifically comprises the following steps in sequence in the measuring process:
(1) Under the stable ambient temperature, respectively flushing calibration gas into the first optical cavity 8 and the second optical cavity 11, controlling the DBF laser 1 to emit laser beams with specific wavelengths, and after the laser beams enter the optical modulator 2 for modulation, sequentially arranging the first convex mirror 3, the small hole 4 and the second convex mirror 5;
(2) The laser beam passing through the second convex mirror 5 respectively enters the first rectangular prism 6 and the second rectangular prism 9, is divided into two paths, passes through the first filter 7 and the second filter 7, and then respectively enters the first optical cavity 8 and the second optical cavity 11;
(3) The light beams after the first and second optical cavities 8,11 ring down are detected by the first and second detection devices 16, and then sent to the data acquisition processor 18, and the measurement is carried out by utilizing the optical cavity ring down spectroscopy technology;
(4) Comparing the two paths of measurement results, if the difference value is within the threshold range, entering the next step, otherwise, adjusting the system to ensure that the difference value of the two paths of measurement results meets the threshold range, and returning to the step (1);
(5) Starting measurement, respectively flushing target gas into the first optical cavity 8 and the second optical cavity 11, respectively controlling the corresponding first heater 13 and the corresponding second heater 13 in the first optical cavity 8 and the second optical cavity 11 to start heating, simultaneously controlling the corresponding temperature sensing unit 12 to start measurement according to a certain period, and entering the next step when the temperatures in the first optical cavity 8 and the second optical cavity 11 are stabilized within a preset temperature range;
(6) The DBF laser 1 is controlled to emit laser beams with specific wavelength, the laser beams enter the optical modulator 2 for modulation, then enter the first convex mirror 3, the small hole 4 and the second convex mirror 5 in sequence, then enter the first rectangular prism 6 and the second rectangular prism 9 correspondingly, respectively enter the first optical cavity 8 and the second optical cavity 11 after passing through the first filter and the second filter, and after being detected by the first detection device 16 and the second detection device 17, the laser beams are sent to the data acquisition processor 18 for measurement by utilizing the optical cavity ring-down spectroscopy.
In addition, the step (6) further comprises a temperature compensation verification step, wherein target gases respectively flushed in the first optical cavity 8 and the second optical cavity 11 are kept, the corresponding first heater 13 and the corresponding second heater 13 in the first optical cavity 8 and the second optical cavity 11 are respectively controlled to start heating, and the corresponding temperature sensing unit 12 is controlled to start measuring according to a certain period, so that the temperature in the first optical cavity 8 and the second optical cavity 11 reaches another temperature range different from a preset temperature range; and (3) returning to the step (6) when the temperatures in the first and second optical cavities 8 and 11 are stable within another preset temperature range, calculating the influence relation of temperature change on the measurement result according to a theoretical calculation mode, and verifying whether the accuracy of the system meets the requirement.
Although exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions, and the like, can be made in the form and detail without departing from the scope and spirit of the invention as disclosed in the accompanying claims, all such modifications are intended to be within the scope of the invention as disclosed in the accompanying claims, and the various steps of the invention in the various departments and methods of the claimed product can be combined together in any combination. Therefore, the description of the embodiments disclosed in the present invention is not intended to limit the scope of the present invention, but is used to describe the present invention. Accordingly, the scope of the invention is not limited by the above embodiments, but is defined by the claims or equivalents thereof.
Claims (3)
1. The measuring method of the system for detecting the trace methane content in the ultra-high purity gas by utilizing the optical cavity ring-down spectroscopy is characterized in that the system for detecting the trace methane content in the ultra-high purity gas by utilizing the optical cavity ring-down spectroscopy comprises a DBF laser, an optical modulator, a first convex mirror, a small hole and a second convex mirror which are sequentially arranged on an optical axis;
the two rectangular prisms are respectively arranged on reflection curves of the laser emission direction of the DBF laser and the detection directions of the objects of the two target optical cavities, and the laser beams passing through the second convex mirror are respectively reflected in the first rectangular prism and the second rectangular prism for multiple times and then emitted in the detection directions of the objects of the two target optical cavities;
the rear end of the first rectangular prism is also provided with a first filter, a first optical cavity, a first detection device and a second filter, the second optical cavity, the second detection device and the first detection device are respectively connected with a data acquisition processor;
the two sides of the inner bottoms of the first optical cavity and the second optical cavity are respectively and correspondingly provided with a first heater and a second heater, the first heater and the second heater are respectively connected with a temperature controller, and the temperature controller is also connected with a data acquisition processor;
the inner bottoms of the first optical cavity and the second optical cavity are respectively provided with a heating layer, and the first heater and the second heater are arranged in the heating layers;
one side of the inner top parts of the first optical cavity and the second optical cavity is respectively and correspondingly provided with a temperature sensing unit which is respectively connected with a temperature detector;
the measuring method sequentially comprises the following steps:
(1) Under the stable ambient temperature, respectively filling calibration gas into the first optical cavity and the second optical cavity, controlling the DBF laser to emit laser beams with specific wavelengths, and enabling the laser beams to sequentially pass through the first convex mirror, the small hole and the second convex mirror after entering the optical modulator for modulation;
(2) The laser beam passing through the second convex mirror respectively enters the first rectangular prism and the second rectangular prism, is divided into two paths, passes through the first filter plate and the second filter plate and respectively enters the first optical cavity and the second optical cavity;
(3) The light beams after the first and second cavity ring-down are detected by the first and second detection devices respectively and then sent to a data acquisition processor, and the measurement is carried out by utilizing the cavity ring-down spectroscopy;
(4) Comparing the two paths of measurement results, if the difference value is within the threshold range, entering the next step, otherwise, adjusting the system to ensure that the difference value of the two paths of measurement results meets the threshold range, and returning to the step (1);
(5) Starting measurement, respectively filling target gas into the first optical cavity and the second optical cavity, respectively controlling the corresponding first heater and the corresponding second heater in the first optical cavity and the second optical cavity to start heating, simultaneously controlling the corresponding temperature sensing unit to start measurement according to a certain period, and entering the next step when the temperatures in the first optical cavity and the second optical cavity are stabilized within a preset temperature range;
(6) The DBF laser is controlled to emit laser beams with specific wavelength, the laser beams enter the optical modulator to be modulated, then sequentially pass through the first convex lens, the small hole and the second convex lens, correspondingly enter the first rectangular prism and the second rectangular prism, respectively pass through the first filter and the second filter and then enter the first optical cavity and the second optical cavity, and after being detected by the first detection device and the second detection device, the laser beams are sent to the data acquisition processor and are measured by utilizing the optical cavity ring-down spectroscopy technology.
2. The method of claim 1, wherein: the step (6) further comprises a temperature compensation verification step: the method comprises the steps of keeping target gases respectively filled in two paths of first and second optical cavities, respectively controlling corresponding first and second heaters in the first and second optical cavities to start heating, and simultaneously controlling corresponding temperature sensing units to start measuring according to a certain period, so that the temperatures in the first and second optical cavities reach another temperature range different from a preset temperature range; and (3) returning to the step (6) when the temperatures in the first optical cavity and the second optical cavity are stable within another preset temperature range, calculating the influence relation of the temperature change on the measurement result according to a theoretical calculation mode, and verifying whether the precision of the system meets the requirement.
3. The method of claim 1, wherein: the first and second heaters are specifically heating wires or Bohr patches.
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