CN109632681B - Method for detecting sulfur dioxide in ambient air - Google Patents
Method for detecting sulfur dioxide in ambient air Download PDFInfo
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- CN109632681B CN109632681B CN201811638355.8A CN201811638355A CN109632681B CN 109632681 B CN109632681 B CN 109632681B CN 201811638355 A CN201811638355 A CN 201811638355A CN 109632681 B CN109632681 B CN 109632681B
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- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 title claims abstract description 192
- 239000012080 ambient air Substances 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000001514 detection method Methods 0.000 claims abstract description 30
- 238000010521 absorption reaction Methods 0.000 claims abstract description 28
- 238000001228 spectrum Methods 0.000 claims abstract description 23
- 238000000862 absorption spectrum Methods 0.000 claims abstract description 17
- 239000013307 optical fiber Substances 0.000 claims abstract description 17
- 238000002211 ultraviolet spectrum Methods 0.000 claims abstract description 17
- 235000010269 sulphur dioxide Nutrition 0.000 claims description 87
- 239000007789 gas Substances 0.000 claims description 80
- 239000013598 vector Substances 0.000 claims description 27
- 230000002452 interceptive effect Effects 0.000 claims description 15
- 230000003595 spectral effect Effects 0.000 claims description 13
- 238000002835 absorbance Methods 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 3
- 238000009499 grossing Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 239000004291 sulphur dioxide Substances 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 description 10
- 239000003570 air Substances 0.000 description 8
- 238000002795 fluorescence method Methods 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002848 electrochemical method Methods 0.000 description 1
- 238000001917 fluorescence detection Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Classifications
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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
- G01N21/33—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using ultraviolet light
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention provides an ambient air sulfur dioxide detection device and a detection method, wherein the ambient air sulfur dioxide detection device comprises a gas absorption chamber, the gas absorption chamber comprises a lens barrel, a first reflecting mirror and a second reflecting mirror, the lens barrel further comprises a first end and a second end, the first reflecting mirror is arranged at the first end of the lens barrel, and the second reflecting mirror is arranged at the second end of the lens barrel; the center of the first reflecting mirror is provided with a through hole, a planoconvex lens is arranged in the through hole, the planoconvex lens comprises a plane side and a convex side, the planoconvex lens further comprises a deep ultraviolet continuous spectrum light source, a data processor and an optical fiber branching device, and the data processor collects deep ultraviolet light and calculates sulfur dioxide concentration; according to the invention, the absorption spectrum is calculated by utilizing the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air, the sulfur dioxide concentration in the ambient air is calculated by adopting a Fourier transform and polynomial fitting method, and meanwhile, the influence of the interference gas on the sulfur dioxide concentration is eliminated, so that the anti-interference capability of detection is improved.
Description
Technical Field
The invention belongs to the technical field of gas detection, and particularly relates to an ambient air sulfur dioxide detection device and method.
Background
Sulfur dioxide is a major environmental air contaminant and is a necessary measure of environmental air gaseous contaminant monitoring. The prior method for measuring sulfur dioxide mainly comprises an ultraviolet fluorescence method, an electrochemical method, a chemiluminescence method, an atomic absorption method and the like. The ultraviolet fluorescence method becomes one of standard methods by virtue of the advantages of high sensitivity, good selectivity, large measurement range, no need of chemical reagents, real-time online measurement and the like, and is particularly suitable for the application of an atmosphere continuous monitoring system with low sulfur dioxide concentration. A large number of sulfur dioxide monitors based on ultraviolet fluorescence methods of American API companies and Thermo companies are introduced in China for online monitoring of sulfur dioxide in ambient air. However, the ultraviolet fluorescence method also has some problems in detecting sulfur dioxide, such as easy interference of fluorescence generated by Hydrocarbon (HC) compounds in the air, easy fluorescence quenching, and the like, which influence the detection result. In addition, fluorescence detection belongs to very weak signal detection and single parameter detection, and has poor anti-interference capability. A high precision gas path design is required, and a gas absorption chamber is one of key components of an optical absorption method gas sensor for detecting trace gases. In the optical absorption gas sensor, the longer the optical path length of the gas cell is, the lower the concentration of the gas that can be detected is. However, in the existing gas absorption chamber design scheme, the longer the optical path is, the larger the volume of the gas chamber is, the response capability is reduced, the relative aperture is reduced, the light energy loss is serious, and a light source with higher power is required. The gas absorption chamber with long optical path, small volume and large relative aperture is designed, and has important function for improving the performance of the gas sensor by an optical absorption method.
In view of the foregoing, it is necessary to provide an ambient air sulfur dioxide detection device and detection method that have a strong anti-interference capability and a gas absorption chamber that has the characteristics of long optical path length, small volume, and large relative aperture.
Disclosure of Invention
Aiming at the technical problems, the invention provides an ambient air sulfur dioxide detection device and method with strong anti-interference capability and the characteristics of long optical path length, small volume and large relative aperture of a gas absorption chamber.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the device for detecting sulfur dioxide in ambient air comprises a gas absorption chamber, wherein the gas absorption chamber comprises a lens barrel, a first reflecting mirror and a second reflecting mirror, a gas inlet and a gas outlet are formed in the lens barrel, the lens barrel further comprises a first end and a second end, the first reflecting mirror is arranged at the first end of the lens barrel, and the second reflecting mirror is arranged at the second end of the lens barrel; the center of the first reflecting mirror is provided with a through hole, a plano-convex lens is arranged in the through hole, the plano-convex lens comprises a plane side and a convex side, the plane side of the plano-convex lens is close to the lens barrel, and the convex side of the plano-convex lens is away from the lens barrel;
the ambient air sulfur dioxide detection device further comprises a deep ultraviolet continuous spectrum light source, a data processor and an optical fiber branching device, wherein the deep ultraviolet continuous spectrum light source is connected with the through hole through the optical fiber branching device so as to enable deep ultraviolet light to enter the lens cone from the planoconvex lens, and the data processor is connected with the through hole through the optical fiber branching device so as to collect the deep ultraviolet light reflected by the second reflecting mirror and the first reflecting mirror and then emitted from the planoconvex lens and calculate sulfur dioxide concentration.
Preferably, the data processor includes:
a data acquisition unit: the device is used for collecting the deep ultraviolet spectrum emitted from the plano-convex lens after being reflected by the second reflecting mirror and the first reflecting mirror;
a calibration formula calculation unit: the method comprises the steps of calculating a calibration formula based on absorbance information of sulfur dioxide standard gas and interfering object standard gas, wherein the sulfur dioxide standard gas is sulfur dioxide gas with known concentration, and the interfering object standard gas is interfering object gas with known concentration;
sulfur dioxide concentration calculation unit: and the sulfur dioxide concentration is calculated based on the absorbance information of the measured ambient air and the calibration formula calculated by the calibration formula calculation unit.
Preferably, the first reflecting mirror and the second reflecting mirror are coaxially arranged, the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are arranged in a face-to-face manner, and reflecting films are plated on the reflecting surfaces of the first reflecting mirror and the second reflecting mirror.
Preferably, the reflecting surfaces of the first and second reflecting mirrors are concave surfaces, the radius of curvature of the reflecting surfaces of the first and second reflecting mirrors is the same, and the diameters of the first and second reflecting mirrors are the same.
Preferably, a window is further installed in the through hole, the window is made of planar glass, the through hole comprises a first through hole and a second through hole, and the window is arranged in the first through hole and covers the orifice of the second through hole.
Preferably, the plano-convex lens is disposed in the first through hole, and the louver is disposed laterally to a planar side of the plano-convex lens.
Preferably, the surface of the window sheet is coated with a bandpass film.
Preferably, the optical fiber splitter adopts a Y-type optical fiber.
The method for detecting the sulfur dioxide in the ambient air adopts the device for detecting the sulfur dioxide in the ambient air, and comprises the following steps:
s1, collecting deep ultraviolet reference spectrum absorbed by pollution-free gas;
s2, collecting a deep ultraviolet spectrum absorbed by ambient air, and performing dark current removal, wavelength calibration and spectrum smoothing pretreatment on the collected deep ultraviolet spectrum;
s3, calculating an absorption spectrum by using the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air;
step S4, extracting spectral characteristics T= [ T ] after Fourier transform of sulfur dioxide absorption wave bands in absorption spectrum 1 ,t 2 ,...t n ]Spectral feature d= [ D ] of interferent gas absorption band 1 ,d 2 ,...d m ]Wherein T is a 1×n vector, D is 1×m, n and m represent feature numbers;
step S5, combining the extracted sulfur dioxide spectral feature T with the spectral feature D of the interfering gas to obtain a feature combination vector TD= [ T, D ]]＝[t 1 ,t 2 ,...t n ,d 1 ,d 2 ,...d m ]TD is a 1× (n+m) vector;
step S6, calculating the concentration relative value Cx=TD. Uso of sulfur dioxide according to the characteristic combination vector TD 2 In which Uso is 2 Is a characteristic determinant and is obtained by a calibration process;
s7, calculating the concentration C of the sulfur dioxide according to the relative concentration value of the sulfur dioxide and a calibration fitting formula SO2 = kCx +b, where k and b are the calibration coefficients, resulting from the calibration process.
Preferably, the calibration process comprises the steps of:
measuring the absorption spectrum of sulfur dioxide standard gas under different concentrations, and recording the concentration as c i (i=1, 2,3,..p.) p represents the number of sulphur dioxide gas concentrations, and feature combination vectors TD of different known concentrations are obtained according to said steps S1 to S5 i ＝[t i1 ,t i2 ,...t in ,d i1 ,d i2 ,...d im ]；
Measuring the absorption spectrum of the interference object standard gas under different concentrations, and recording the concentration as c j (j=1, 2,3,..q.) q represents the number of concentrations of the interfering gas, and the feature combination vector TD of different known concentrations is obtained according to said steps S1 to S5 j ＝[t j1 ,t j2 ,...t jn ,d j1 ,d j2 ,...d jm ]；
For TD i Normalizing the concentration to obtain TD i /c i ＝[t i1 /c i ,t i2 /c i ,...t in /c i ,d i1 /c i ,d i2 /c i ,...d im /c i ]Taking the average value of the feature combination vectors normalized by different known concentrations as
For TD j Normalizing the concentration to obtain TD j /c j ＝[t j1 /c j ,t j2 /c j ,...t jn /c j ,d j1 /c j ,d j2 /c j ,...d jm /c j ]Taking the average value of the feature combination vectors normalized by different known concentrations as
Will S so2 And S is distrub Composition 2× (n+m) feature determinant ss= [ S ] so2 ；S disturb ]Further, u=inv (SS '×ss) ×ss', U is (n+m) ×2 determinant，Uso 2 Taking a first column vector of U;
based on the calculated Uso 2 Calculating the relative concentration Cx of sulfur dioxide standard gases with different known concentrations i ＝TD i *Uso 2 And then, calculating values of the calibration coefficients k and b by using a polynomial fitting method by using relative concentration values and standard concentrations of sulfur dioxide standard gases with different known concentrations.
The invention has the advantages and positive effects that:
1. according to the method for detecting the sulfur dioxide in the ambient air, disclosed by the invention, the absorption spectrum is calculated by utilizing the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air, the sulfur dioxide concentration in the ambient air is calculated by adopting a Fourier transform and polynomial fitting method, and meanwhile, the influence of the interference object gas on the sulfur dioxide concentration is eliminated, so that the anti-interference capability of detection is improved;
2. according to the ambient air sulfur dioxide detection device, the plane convex lens is arranged in the through hole, so that the relative aperture of the whole air chamber is improved, and the energy utilization rate is higher;
3. according to the environmental air sulfur dioxide detection device, the first reflecting mirror and the second reflecting mirror which are arranged face to face can realize multiple reflection, so that the gas absorption chamber has the characteristics of long optical path and small volume.
Drawings
FIG. 1 is a schematic view of a gas absorption chamber according to the present invention;
FIG. 2 is a schematic view of a partial structure of a gas absorption chamber according to the present invention;
FIG. 3 is a schematic view of a plano-convex lens of a gas absorption chamber according to the present invention;
FIG. 4 is a characteristic absorption spectrum of sulfur dioxide in the deep ultraviolet spectrum of the present invention;
FIG. 5 is a Fourier transform spectrum of the characteristic absorption spectrum of sulfur dioxide in the deep ultraviolet spectrum of the present invention;
FIG. 6 is a schematic diagram of a data processor according to the present invention;
fig. 7 is a schematic structural diagram of the sulfur dioxide detection device for the ambient air in the invention.
In the figure: 1. a first mirror; 11. a through hole; 111. a first through hole; 112. a second through hole; 12. a plano-convex lens; 121. a planar side; 122. a convex side; 13. a window pane; 2. a second mirror; 3. a lens barrel; 31. a first end; 32. a second end; 4. a deep ultraviolet continuous spectrum light source; 5. a data processor; 51. a data acquisition unit; 52. a calibration formula calculation unit; 53. a sulfur dioxide concentration calculation unit; 6. an optical fiber splitter.
Detailed Description
The present invention will be specifically described below by way of exemplary embodiments. It is to be understood that elements, structures, and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
In the description of the present invention, it should be noted that the positional or positional relationship indicated by the terms such as "inner", "outer", "upper", "lower", "front", "rear", etc. are based on the positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
As shown in fig. 1, a gas absorbing chamber comprises a lens barrel 3, a first reflecting mirror 1 and a second reflecting mirror 2, wherein a gas inlet and a gas outlet are formed in the lens barrel 3, the lens barrel 3 comprises a first end 31 and a second end 32, the first reflecting mirror 1 is arranged at the first end 31 of the lens barrel 3, and the second reflecting mirror 2 is arranged at the second end 32 of the lens barrel 3; a through hole 11 is formed in the center of the first reflecting mirror 1, a plano-convex lens 12 is installed in the through hole 11, the plano-convex lens 12 comprises a plane side 121 and a convex side 122, the plane side 121 of the plano-convex lens 12 is arranged close to the lens barrel 3, and the convex side 122 of the plano-convex lens 12 is arranged away from the lens barrel 3; the light beam entering the lens barrel 3 from the plano-convex lens 12 is reflected by the second reflecting mirror 2 and the first reflecting mirror 1 and then is emitted from the plano-convex lens 12, the plano-convex lens 12 is used for converging the light beam, the relative aperture of the gas absorption chamber is improved, the light energy utilization rate is further improved, the light beam is reflected and converged between the first reflecting mirror 1 and the second reflecting mirror 2 for multiple times, the reflecting times of the light beam between the first reflecting mirror 1 and the second reflecting mirror 2 can be changed by adjusting the center distance between the first reflecting mirror 1 and the second reflecting mirror 2, and therefore the optical path is changed.
The utility model provides an ambient air sulfur dioxide detection device, includes the gas absorption room, the gas absorption room includes barrel 3, first speculum 1 and second speculum 2, air inlet and gas outlet have been seted up on the barrel 3, the barrel 3 still includes first end 31 and second end 32, first speculum 1 sets up in the first end 31 of barrel 3, second speculum 2 sets up in the second end 32 of barrel 3; a through hole 11 is formed in the center of the first reflecting mirror 1, a plano-convex lens 12 is installed in the through hole 11, the plano-convex lens 12 comprises a plane side 121 and a convex side 122, the plane side 121 of the plano-convex lens 12 is arranged close to the lens barrel, and the convex side 122 of the plano-convex lens 12 is arranged away from the lens barrel 3;
the ambient air sulfur dioxide detection device further comprises a deep ultraviolet continuous spectrum light source 4, a data processor 5 and an optical fiber branching device 6, wherein the deep ultraviolet continuous spectrum light source 4 is connected with the through hole 11 through the optical fiber branching device 6 so as to enable deep ultraviolet light to enter the lens cone 3 from the plano-convex lens 12, and the deep ultraviolet continuous spectrum light source 4 emits the deep ultraviolet light with continuous spectrum power distribution at 200 nm-210 nm; the data processor 5 is connected with the through hole 11 through the optical fiber splitter 6 to collect the deep ultraviolet light reflected by the second reflecting mirror 2 and the first reflecting mirror 1 and then emitted from the plano-convex lens 12 and calculate the sulfur dioxide concentration, and the optical fiber splitter 6 is preferably a Y-type optical fiber.
Further, the data processor 5 includes:
a data acquisition unit 51: the device is used for collecting the deep ultraviolet spectrum emitted from the plano-convex lens after being reflected by the second reflecting mirror and the first reflecting mirror;
calibration formula calculation unit 52: the method comprises the steps of calculating a calibration formula based on absorbance information of sulfur dioxide standard gas and interfering object standard gas, wherein the sulfur dioxide standard gas is sulfur dioxide gas with known concentration, and the interfering object standard gas is interfering object gas with known concentration;
sulfur dioxide concentration calculation unit 53: the calibration formula calculation unit is used for calculating the concentration of sulfur dioxide based on the absorbance information of the measured ambient air and the calibration formula calculated by the calibration formula calculation unit
Further, the first reflecting mirror 1 and the second reflecting mirror 2 are coaxially arranged, and the reflecting surface of the first reflecting mirror 1 and the reflecting surface of the second reflecting mirror 2 are arranged in a face-to-face manner; further, the reflecting surfaces of the first reflecting mirror 1 and the second reflecting mirror 2 are concave surfaces, the radius of curvature of the reflecting surfaces of the first reflecting mirror 1 and the second reflecting mirror 2 is the same, the diameters of the first reflecting mirror 1 and the second reflecting mirror 2 are the same, and reflecting films are plated on the reflecting surfaces of the first reflecting mirror 1 and the second reflecting mirror 2 for realizing better emitting effect.
As shown in fig. 2, a window 13 is further installed in the through hole 11, the window 13 is a planar glass, the through hole 11 includes a first through hole 111 and a second through hole 112, the window 13 is disposed in the first through hole 111 and covers the orifice of the second through hole 112 for sealing the air chamber, the surface of the window 13 is coated with a band-pass film to balance the spectral transmittance of the air absorbing chamber, reduce stray light, the plano-convex lens 12 is disposed in the first through hole 111, and the window 13 is disposed at a side of the planar side 121 of the plano-convex lens 12.
The method for detecting the sulfur dioxide in the ambient air adopts the device for detecting the sulfur dioxide in the ambient air, and comprises the following steps:
s1, collecting deep ultraviolet reference spectrum absorbed by pollution-free gas;
s2, collecting a deep ultraviolet spectrum absorbed by ambient air, and performing dark current removal, wavelength calibration and spectrum smoothing pretreatment on the collected deep ultraviolet spectrum;
s3, calculating an absorption spectrum by using the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air;
step S4, extracting spectral characteristics T= [ T ] after Fourier transform of sulfur dioxide absorption wave bands in absorption spectrum 1 ,t 2 ,...t n ]Spectral feature d= [ D ] of interferent gas absorption band 1 ,d 2 ,...d m ]Wherein T is a 1×n vector, D is 1×m, n and m represent feature numbers;
step S5, combining the extracted sulfur dioxide spectral feature T with the spectral feature D of the interfering gas to obtain a feature combination vector TD= [ T, D ]]＝[t 1 ,t 2 ,...t n ,d 1 ,d 2 ,...d m ]TD is a 1× (n+m) vector;
step S6, calculating the concentration relative value Cx=TD. Uso of sulfur dioxide according to the characteristic combination vector TD 2 In which Uso is 2 Is a characteristic determinant and is obtained by a calibration process;
s7, calculating the concentration C of the sulfur dioxide according to the relative concentration value of the sulfur dioxide and a calibration fitting formula SO2 = kCx +b, where k and b are the calibration coefficients, resulting from the calibration process.
Further, the calibration process comprises the following steps:
measuring the absorption spectrum of sulfur dioxide standard gas under different concentrations, and recording the concentration as c i (i=1, 2,3,..p.) p represents the number of sulphur dioxide gas concentrations, and feature combination vectors TD of different known concentrations are obtained according to said steps S1 to S5 i ＝[t i1 ,t i2 ,...t in ,d i1 ,d i2 ,...d im ]；
Measuring the absorption spectrum of the interference object standard gas under different concentrations, and recording the concentration as c j (j=1, 2,3,..q.) q represents the number of concentrations of the interfering gas, and the feature combination vector TD of different known concentrations is obtained according to said steps S1 to S5 j ＝[t j1 ,t j2 ,...t jn ,d j1 ,d j2 ,...d jm ]；
For TD i Normalizing the concentration to obtain TD i /c i ＝[t i1 /c i ,t i2 /c i ,...t in /c i ,d i1 /c i ,d i2 /c i ,...d im /c i ]Taking the average value of the feature combination vectors normalized by different known concentrations as
For TD j Normalizing the concentration to obtain TD j /c j ＝[t j1 /c j ,t j2 /c j ,...t jn /c j ,d j1 /c j ,d j2 /c j ,...d jm /c j ]Taking the average value of the feature combination vectors normalized by different known concentrations as
Will S so2 And S is distrub Composition 2× (n+m) feature determinant ss= [ S ] so2 ；S disturb ]Further, u=inv (SS '×ss) ×ss', U is a (n+m) ×2 determinant, uso 2 Taking a first column vector of U;
based on the calculated Uso 2 Calculating the relative concentration Cx of sulfur dioxide standard gases with different known concentrations i ＝TD i *Uso 2 And then, calculating values of the calibration coefficients k and b by using a polynomial fitting method by using relative concentration values and standard concentrations of sulfur dioxide standard gases with different known concentrations.
According to the method for detecting the sulfur dioxide in the ambient air, disclosed by the invention, the absorption spectrum is calculated by utilizing the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air, the sulfur dioxide concentration in the ambient air is calculated by adopting a Fourier transform and polynomial fitting method, and meanwhile, the influence of the interference object gas on the sulfur dioxide concentration is eliminated, so that the anti-interference capability of detection is improved.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; while the invention has been described in detail with reference to the foregoing embodiments, it will be appreciated by those skilled in the art that variations may be made in the techniques described in the foregoing embodiments, or equivalents may be substituted for elements thereof; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. The method for detecting sulfur dioxide in the ambient air is characterized by comprising the following steps of: detecting by adopting an ambient air sulfur dioxide detection device; the ambient air sulfur dioxide detection device comprises a gas absorption chamber, wherein the gas absorption chamber comprises a lens barrel, a first reflecting mirror and a second reflecting mirror, the lens barrel is provided with a gas inlet and a gas outlet, the lens barrel further comprises a first end and a second end, the first reflecting mirror is arranged at the first end of the lens barrel, and the second reflecting mirror is arranged at the second end of the lens barrel; the center of the first reflecting mirror is provided with a through hole, a plano-convex lens is arranged in the through hole, the plano-convex lens comprises a plane side and a convex side, the plane side of the plano-convex lens is close to the lens barrel, and the convex side of the plano-convex lens is away from the lens barrel;
the ambient air sulfur dioxide detection device further comprises a deep ultraviolet continuous spectrum light source, a data processor and an optical fiber branching device, wherein the deep ultraviolet continuous spectrum light source is connected with the through hole through the optical fiber branching device so as to enable deep ultraviolet light to enter the lens barrel from the planoconvex lens, and the data processor is connected with the through hole through the optical fiber branching device so as to collect the deep ultraviolet light reflected by the second reflecting mirror and the first reflecting mirror and then emitted from the planoconvex lens and calculate the concentration of sulfur dioxide;
the detection method comprises the following steps:
s1, collecting deep ultraviolet reference spectrum absorbed by pollution-free gas;
s2, collecting a deep ultraviolet spectrum absorbed by ambient air, and performing dark current removal, wavelength calibration and spectrum smoothing pretreatment on the collected deep ultraviolet spectrum;
s3, calculating an absorption spectrum by using the reference spectrum and the deep ultraviolet spectrum absorbed by the ambient air;
step S4, extracting spectral characteristics T= [ T ] after Fourier transform of sulfur dioxide absorption wave bands in absorption spectrum 1 ,t 2 ,...t n ]Spectral feature d= [ D ] of interferent gas absorption band 1 ,d 2 ,...d m ]Wherein T is a 1×n vector, D is 1×m, n and m represent feature numbers;
step S5, combining the extracted sulfur dioxide spectral feature T with the spectral feature D of the interfering gas to obtain a feature combination vector TD= [ T, D ]]＝[t 1 ,t 2 ,...t n ,d 1 ,d 2 ,...d m ]TD is a 1× (n+m) vector;
step S6, calculating the concentration relative value Cx=TD. Uso of sulfur dioxide according to the characteristic combination vector TD 2 In which Uso is 2 Is a characteristic determinant and is obtained by a calibration process;
s7, calculating the concentration C of the sulfur dioxide according to the relative concentration value of the sulfur dioxide and a calibration fitting formula SO2 = kCx +b, where k and b are the calibration coefficients, resulting from the calibration process.
2. The ambient air sulfur dioxide detection method of claim 1, wherein: the data processor includes:
a data acquisition unit: the device is used for collecting the deep ultraviolet spectrum emitted from the plano-convex lens after being reflected by the second reflecting mirror and the first reflecting mirror;
a calibration formula calculation unit: the method comprises the steps of calculating a calibration formula based on absorbance information of sulfur dioxide standard gas and interfering object standard gas, wherein the sulfur dioxide standard gas is sulfur dioxide gas with known concentration, and the interfering object standard gas is interfering object gas with known concentration;
sulfur dioxide concentration calculation unit: and the sulfur dioxide concentration is calculated based on the absorbance information of the measured ambient air and the calibration formula calculated by the calibration formula calculation unit.
3. The ambient air sulfur dioxide detection method of claim 1, wherein: the first reflecting mirror and the second reflecting mirror are coaxially arranged, the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are arranged in a face-to-face mode, and reflecting films are plated on the reflecting surfaces of the first reflecting mirror and the second reflecting mirror.
4. A method for ambient air sulfur dioxide detection according to claim 3, wherein: the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are concave surfaces, the curvature radiuses of the reflecting surfaces of the first reflecting mirror and the second reflecting mirror are the same, and the diameters of the first reflecting mirror and the second reflecting mirror are the same.
5. The ambient air sulfur dioxide detection method of claim 1, wherein: and a window sheet is further installed in the through hole and is made of planar glass, the through hole comprises a first through hole and a second through hole, and the window sheet is arranged in the first through hole and covers the orifice of the second through hole.
6. The method for detecting sulfur dioxide in ambient air according to claim 5, wherein: the plano-convex lens is arranged in the first through hole, and the window piece is arranged at the side of the plane side of the plano-convex lens.
7. The method for detecting sulfur dioxide in ambient air according to claim 5, wherein: and the surface of the window sheet is plated with a band-pass film.
8. The ambient air sulfur dioxide detection method of claim 1, wherein: the optical fiber branching device adopts Y-shaped optical fibers.
9. The ambient air sulfur dioxide detection method of claim 1, wherein: the calibration process comprises the following steps:
measuring the absorption spectrum of sulfur dioxide standard gas under different concentrations, and recording the concentration as c i (i=1, 2,3,..p.) p represents the number of sulphur dioxide gas concentrations, and feature combination vectors TD of different known concentrations are obtained according to said steps S1 to S5 i ＝[t i1 ,t i2 ,...t in ,d i1 ,d i2 ,...d im ]；
Measuring the absorption spectrum of the interference object standard gas under different concentrations, and recording the concentration as c j (j=1, 2,3,..q.) q represents the number of concentrations of the interfering gas, and the feature combination vector TD of different known concentrations is obtained according to said steps S1 to S5 j ＝[t j1 ,t j2 ,...t jn ,d j1 ,d j2 ,...d jm ]；
For TD i Normalizing the concentration to obtain TD i /c i ＝[t i1 /c i ,t i2 /c i ,...t in /c i ,d i1 /c i ,d i2 /c i ,...d im /c i ]Taking the average value of the feature combination vectors normalized by different known concentrations as
For TD j Normalizing the concentration to obtain TD j /c j ＝[t j1 /c j ,t j2 /c j ,...t jn /c j ,d j1 /c j ,d j2 /c j ,...d jm /c j ]Taking the average value of the feature combination vectors normalized by different known concentrations as
Will S so2 And S is distrub Composition 2× (n+m) feature determinant ss= [ S ] so2 ；S disturb ]Further, u=inv (SS '×ss) ×ss', U is a (n+m) ×2 determinant, uso 2 Taking a first column vector of U;
based on the calculated Uso 2 Calculating the relative concentration of sulfur dioxide standard gases with different known concentrationsValue Cx i ＝TD i *Uso 2 And then, calculating values of the calibration coefficients k and b by using a polynomial fitting method by using relative concentration values and standard concentrations of sulfur dioxide standard gases with different known concentrations.
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