Method for improving differential absorption spectrum on-line monitoring sensitivity

A technology of differential absorption spectroscopy and monitoring sensitivity, applied in absorption/scintillation/reflection spectroscopy, color/spectral characteristic measurement, spectrum investigation, etc., which can solve problems such as effective signal overlap, difficulty in low-pass characteristics, and no basis for selection judgment.

Inactive Publication Date: 2010-06-09
TIANJIN UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the overlapping of effective signal and fast-changing characteristics of noise makes the selection of low-pass characteristics not only difficult, but also has no basis for selection and judgment. In different applications, trial and error methods are often used to find suitable filter characteristics. This trial and error method is blind Disadvantages such as sexuality and excessive workload

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  • Method for improving differential absorption spectrum on-line monitoring sensitivity
  • Method for improving differential absorption spectrum on-line monitoring sensitivity
  • Method for improving differential absorption spectrum on-line monitoring sensitivity

Examples

Experimental program
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Effect test

Embodiment 1

[0059] In the continuous monitoring system of flue gas emissions from fixed pollution sources, the gaseous pollutants in flue gas emissions—sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ) and nitric oxide (NO) were monitored online by differential absorption spectroscopy.

[0060] Such as the standard absorption cross section of sulfur dioxide in the range of 200-250nm (such as figure 1 Shown) do frequency domain transformation, get the frequency domain map as figure 2 shown by figure 2 OK SO 2 The characteristic change interval of the gas is (0.5-0.8cm -1 ).

[0061] For example, the standard absorption cross section of nitrogen dioxide in the range of 200-250nm (such as image 3 Shown) do frequency domain transformation, get the frequency domain map as Figure 4 shown by Figure 4 OK NO 2 The characteristic change interval of the gas is (0.16-0.2cm -1 ).

[0062] For example, the standard absorption cross section of nitric oxide in the range of 200-250nm (such ...

Embodiment 2

[0069] As shown in Example 1, in the continuous monitoring system for flue gas emissions from fixed pollution sources, the gaseous pollutants in the flue gas emissions—sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ) and nitric oxide (NO) were monitored online by differential absorption spectroscopy.

[0070] For example, the standard absorption cross sections of sulfur dioxide, nitrogen dioxide, and nitrogen monoxide in the range of 200-250nm (respectively as figure 1 , 3 and 5) do frequency domain transformation to obtain frequency domain diagrams as figure 2 , 4 As shown in and 6, it can be determined that the total characteristic changes of the three gases of sulfur dioxide, nitrogen dioxide and nitrogen monoxide are two intervals (0.07-0.3cm -1 ) and (0.6-0.7cm -1 ), so the comb filter can be used to analyze the spectrum Figure 10 Carry out data processing, and the SO can be calculated by formula (8) 2 Concentration measured as SO 2 is 422ppm and NO is 205ppm. ...

Embodiment 3

[0072] In the air quality monitoring system, the trace gas benzene (C 6 h 6 ), formaldehyde (HCHO), ozone (O 3 ), sulfur dioxide (SO 2 ) and so on for long optical path measurements.

[0073] Perform frequency domain transformation on the standard absorption cross section of benzene in the range of 239-270nm, and determine the characteristic change of benzene from the frequency domain diagram to be 0.16-5cm -1 .

[0074] Perform frequency domain transformation on the standard absorption cross section of formaldehyde in the range of 250-356nm, and determine the characteristic change of formaldehyde from the frequency domain diagram to be 0.07-0.2cm -1 .

[0075] Perform frequency domain transformation on the standard absorption cross section of ozone in the range of 240-300nm, and determine the characteristic change of ozone from the frequency domain diagram to be 0.26-0.6cm -1 .

[0076] Perform frequency domain transformation on the standard absorption cross section of...

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Abstract

The invention relates to a method for improving differential absorption spectrum on-line monitoring sensitivity, which comprises the following steps of: carrying out characteristic change extraction of the same characteristic on a gas standard absorption section and measured spectroscopic data, and carrying out computation of gas components and concentration on the basis of characteristic change data. The characteristic change of gas absorption spectrums is a point or a range of energy spectrum concentration in a standard absorption section frequency domain graph, and the characteristic change comprises a slowly changing point uL and a fast changing point vH. Band-pass processing with the passbands as uL and vH is carried out on the gas standard absorption section to obtain the characteristic change, and smoothing (low-pass) processing of the fast changing point vH is carried out on the measured spectroscopic data to obtain equivalent emergent light intensity I'(lambda). The invention can effectively eliminate the influences of various noises and interferences on on-line measurement, reserve the part having the greatest contribution to the signal-to-noise ratio and the detection sensitivity in signals, can find an optimal demarcation point of signal processing without using a trial and error method, and finally improve the on-line integrating precision and sensitivity of a differential absorption spectrometric method.

Description

technical field [0001] The invention relates to a differential absorption spectrum analysis method (DOAS), in particular to a method for improving the online monitoring sensitivity of the differential absorption spectrum. Background technique [0002] The theoretical basis of spectral analysis is the Lambert-Beer law (Lambert-Beer law): [0003] I(λ)=I 0 (λ)exp[-Lσ(λ)c] (1) [0004] Among them: I 0 (λ) is the incident light intensity of the measured substance; I(λ) is the outgoing light intensity; L is the optical path length (cm); c is the gas concentration (mol / cm 3 ); σ(λ) is the absorption cross section (cm 2 / mol), refers to the absorption coefficient of the substance per unit concentration and optical path length. According to formula (1), the concentration of the measured substance can be calculated when the optical path length and absorption cross section are known. [0005] The Lambert-Beer law cannot be directly applied to the analysis of atmospheric spectros...

Claims

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Application Information

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IPC IPC(8): G01N21/31G01J3/42
Inventor 杜振辉马艺闻陈文亮徐可欣
Owner TIANJIN UNIV
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