SU913182A1 - Gas mixture analysis method - Google Patents

Description

The invention relates to gas analysis, namely to interferometric gas analyzers, and can be used when conducting analyzes of multicomponent mixtures.

Known is a method of gas analysis sme- ⁵ this is based on. measuring the difference in refractive indices of the analyzed mixture and the reference medium [1].

The disadvantage of this method is the low sensitivity due to ¹⁰ small differences in the refractive indices of different gases.

The closest to the present invention is a method for analyzing gas mixtures by registering an interference pattern formed by radiation beams that have passed through the analyzed mixture and a reference medium, and determining the concentration of the desired component of the mixture as measured by the interference fringe shift [2].

The disadvantage of this method is its non-selectivity, since it allows

It measures to measure only the concentration of one of the components of a binary mixture and does not allow one to measure the concentration of components in multicomponent mixtures.

The purpose of the invention is to increase the selectivity.

The goal is achieved by the fact that in the method of analyzing gas mixtures, based on registration of the interference pattern formed by radiation beams that have passed through the analyzed mixture and reference medium, and determining the concentration of the desired component of the mixture based on the measurement of the shift of interference fringes, the measurement is performed at an emission wavelength close to to the wavelength

corresponding to the center of the absorption line of the desired component of the mixture at the time when the dispersion of the mixture is zero, and its derivative is negative.

FIG. 1 shows a diagram of a device that implements a method; in fig. 2 graphs of the refractive index and the dispersion of the refractive index3

913182

of the analyzed mixture from the wavelength of the study.

A device that implements the method contains a source of coherent monochromatic radiation with adjustable 5 wavelengths of radiation, a lens 2, a beam splitter 3, a cuvette with a reference medium 4 and the analyzed mixture 5, a mirror 6, combining optics 7, a device for measuring the shift of the interference- 8, a device for measuring the refractive index of the mixture 9, a device for determining the concentration of the components of the mixture 10, a recorder 11 and a device for controlling the length of the radiation wave 12., 5

The device works as follows, / zazom.

Luminous flux from the source 1 of coherent monochromatic radiation with a wavelength A generated obe- ₂₀ ktivom 2, enters the beam splitter 3, where it is divided into two beams, one of which passes through the cell with the test mixture 5 and the other - with reference medium 4. Next, the radiation enters the 25 combining optics 7, where the interference pattern is formed as a result of the difference between the refractive index of the laser radiation source between the reference medium and the mixture being analyzed. The resulting shift of the interference fringes is proportional to - ·. the difference of the refractive indices • Δ And is measured by a device measuring the shift of interference fringes 8, from which information enters the device for determining the concentration of components ^{35 of the} mixture 10. The concentration of the k-th component, that mixture is determined by the formula

 - Yuo A ik

40

(one)

% wherein - the radiation wavelength corresponding to the absorption line of the k-th component of the analyzed ⁴⁵ my mixture;

interference fringe shift;

3 - cuvette length;

the refractive index of the reference medium and. component of the analyzed mixture, respectively.

The refractive index of the reference medium is constant for a given wavelength tuning range of the radiation source 55. The refractive index of the mixture being analyzed νγ _Ν is a function of wavelength and near the absorption line,

dispersed circuit, described by the expression ' ¹

, l - / 1 5 m ί λ IR - λ к

^cm ^ IC-LK) ^g - + (. yhk / 2) ²

where is the wavelength corresponding to the center of the absorption line of the k-th component of the analyzed mixture;

- half-width of the absorption line of the k-th component;

N is the concentration of atoms at the absorbing level;

£ - line oscillator power;

C = 2.24 · 10 ~ ^ cm. ·

From the expression (2) it follows that the tuning of the wavelength L _{and the} source 1 leads to an increase in the refractive index of the analyzed mixture I _C (Fig. 2) as the radiation wavelength approaches

wavelength X _k, corresponding to an absorption line of the k-th component. analyzed mixture. This, in turn, leads to an increase in the difference between the refractive indices between the reference medium and the mixture being analyzed, as well as to an increase in the magnitude of the shift of the interference fringes. In this case, the maximum difference in the refractive indices, and, consequently, the maximum shift of the fringes, is achieved at a certain WAVE length.

Information on the maximum shift of interference fringes ΑΚ · κ _{) Ύ) αχ} for the K-th component of the analyzed mixture is given by the device measuring the shift of the interference fringes 8 to the device for determining the concentration of the mixture components 10 at that moment when the dispersion of the refractive index of the mixture (Zi! S! 1 is equal to zero, and its derivative is negative.

Information about the magnitude of the dispersion is fed to the device to determine the concentration of components 10 from the device for measuring the dispersion of the mixture 9.

Using the wavelength control device 12 for the values of wavelength X * _IR + 1 λ _IR. + 2 and so on, the concentration of the remaining components of the gas mixture is determined.

The use of the proposed method provides the advantages of comparison with the existing methods of gas analysis, which consist in the possibility of analyzing multicomponent gas mixtures using a single device.

913182

Claims (1)

Claim The method of analyzing gas mixtures by registering the interference pattern formed by radiation beams transmitted through the mixture being analyzed and the reference medium, and determining the concentration of the desired component of the mixture as measured by the shift of interference fringes, which differs by '0 in order to increase the selectivity, produce at a wavelength of radiation close to the wavelength, corresponding to the center of the absorption line of the desired component of the mixture at the time when the dispersion of the mixture is zero, and its derivative is negative.