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

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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 judgme

Method used

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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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Example Embodiment

[0058] Example 1:

[0059] In the continuous monitoring system for flue gas emissions from stationary sources, the gaseous pollutant in flue gas emissions—sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), Nitric oxide (NO) is monitored online by differential absorption spectroscopy.

[0060] For example, the standard absorption cross section of sulfur dioxide in the range of 200-250nm (such as figure 1 (Shown) do frequency domain transformation to get a frequency domain map like figure 2 Shown by figure 2 OK SO 2 The characteristic change interval of 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 to get a frequency domain map like Figure 4 Shown by Figure 4 OK NO 2 The characteristic change interval of 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 as Fi...

Example Embodiment

[0068] Example 2:

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

[0070] For example, the standard absorption cross section of sulfur dioxide, nitrogen dioxide, and nitrogen monoxide in the range of 200-250nm (respectively figure 1 , 3 And 5) do frequency domain transformation, and get frequency domain maps 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 nitric oxide are two intervals (0.07-0.3cm -1 ) And (0.6-0.7cm -1 ), the comb filter can be used to Picture 10 Carry out data processing, and calculate the SO value by formula (8) 2 The measured concentration is SO 2 It is 422ppm and NO is 205ppm.

Example Embodiment

[0071] Example 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 measurement.

[0073] The standard absorption cross section of benzene in the range of 239-270nm is transformed in frequency domain, and the characteristic change of benzene is determined to be 0.16-5cm from the frequency domain diagram. -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] The frequency domain transform is performed on the standard absorption cross section of ozone in the range of 240-300nm, and the characteristic change of ozone is determined to be 0.26-0.6cm from the frequency domain diagram. -1 .

[0076] The standard absorption cross section of sulfur dioxide in the range of 260...

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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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