Gas detection method based on absorption spectroscopy

Abstract

This invention provides a gas detection method based on absorption spectroscopy, comprising the following steps: (A1) introducing multiple concentration standard gases into a gas cell and adjusting the pressure within the gas cell to obtain the concentration values ​​C of the multiple concentration standard gases at different pressures. 仪 (A2) Fit the pressure P of the same standard gas to obtain the pressure fitting parameters P′ and C corresponding to the standard gas. 标 It is the nominal concentration of the standard gas; (A3) for the nominal concentration C of the standard gas 标 and its corresponding pressure fitting parameters P The pressure fitting parameters P′ and nominal concentration C are processed to obtain the pressure fitting parameters P′ and C′. 标 Establish and store the correspondence between them; (A4) Introduce the sample gas into the gas cell and obtain the sample gas pressure P in the gas cell. 测 The instrument concentration C of the sample gas was obtained using absorption spectroscopy. 测 The concentration P0 is obtained as atmospheric pressure; (A5) Substituting the concentration C into the corresponding relationship, we obtain the P corresponding to concentration C. 实 Thus, the concentration of the sample gas is obtained. This invention has the advantages of small detection error.

Description

Technical Field

[0001] This invention relates to gas detection, and more particularly to a gas detection method based on absorption spectroscopy. Background Technology

[0002] Non-dispersive infrared (NDIR) technology obtains gas concentration information based on the different absorption rates of different gases for infrared light of different wavelengths.

[0003] Gas concentration measurements based on NDIR technology are highly correlated with gas pressure. For example, if the gas pressure changes from 60 kPa to 130 kPa, the instrument will measure a concentration C. 仪表 With standard gas concentration C 标气 The ratio changed from 40% to 150%. Because the relationship between the absorption spectrum of trace gases and pressure is non-linear under different gas pressures, pressure compensation is generally used in practical NDIR applications, such as:

[0004] 1. Linear proportional pressure compensation method, concentration after compensation C 仪表 P0 is the instrument's original concentration, P0 is atmospheric pressure, and P is the sample gas pressure.

[0005] 2. Power function compensation method, concentration after compensation C 仪表 is the original concentration of the instrument, P is the sample gas pressure, and a and b are the fitting coefficients, respectively.

[0006] 3. Polynomial function compensation method, concentration C after compensation 补偿 = (a+b·P+c·P) 2 +d·P 3 )·C 仪表 C 仪表 P is the original concentration of the instrument, P is the sample gas pressure, and a, b, c, and d are the fitting coefficients.

[0007] The above three compensation algorithms were used to compensate for standard gas concentrations of 10 ppm, 25 ppm, 50 ppm, and 80 ppm, respectively. The compensation results are as follows: Figure 1-4 As shown in the figure, linear proportional compensation performs well when the standard gas concentration is between 10 ppm and 25 ppm; power function compensation and polynomial function compensation methods perform well when the standard gas concentration is between 50 ppm and 80 ppm. However, none of these three methods can achieve efficient compensation for gas concentrations over a wide concentration range of 10 ppm to 80 ppm. Summary of the Invention

[0008] To address the shortcomings of the existing technical solutions, this invention provides a gas detection method based on absorption spectroscopy.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A gas detection method based on absorption spectroscopy includes the following steps.

[0011] (A1) Various concentrations of standard gases are introduced into a gas cell, and the pressure inside the gas cell is adjusted to obtain the concentration values ​​C of the various concentrations of standard gases at different pressures. 仪 ;

[0012] (A2) For the same standard gas By fitting the pressure P of the standard gas, the pressure fitting parameters P′ and C corresponding to the standard gas are obtained. 标 It is the nominal concentration of the standard gas;

[0013] (A3) Nominal concentration of standard gas C 标 The pressure fitting parameter P′ is processed to obtain the pressure fitting parameter P′ and the nominal concentration C. 标 Establish and store the correspondence between them;

[0014] (A4) Introduce the sample gas into the gas cell and obtain the sample gas pressure P in the gas cell. 测 The instrument concentration C of the sample gas was obtained using absorption spectroscopy. 测 To obtain the concentration P0 is atmospheric pressure;

[0015] (A5) Substitute concentration C into the aforementioned correspondence to obtain P corresponding to concentration C. 实 Thus, the sample gas concentration is obtained.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. High detection efficiency;

[0018] The algorithm used in this patent requires fewer parameters to fit compared to traditional power function and exponential function fitting methods, and has a faster running speed and higher detection efficiency.

[0019] 2. Small detection error;

[0020] The algorithm used in this patent can achieve efficient pressure compensation at different concentrations, and the compensation effect is much better than that of the three traditional algorithms. Attached Figure Description

[0021] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are merely illustrative of the technical solutions of this invention and are not intended to limit the scope of protection of this invention. In the drawings:

[0022] Figure 1-4 This is a schematic diagram showing the results of three existing compensation methods for treating gases of different concentrations.

[0023] Figure 5 This is a schematic flowchart of a gas detection method based on absorption spectroscopy according to an embodiment of the present invention;

[0024] Figure 6 This is an embodiment of the present invention. A schematic diagram showing the correspondence between standard gas pressure P and standard gas pressure.

[0025] Figure 7 In the embodiments of the present invention, parameter P′ and nominal concentration C are... 标 A diagram illustrating the correspondence between them;

[0026] Figure 8-11 This is a schematic diagram comparing the method of the present invention and the prior art method at different concentrations;

[0027] Figure 12 This is a schematic diagram comparing the relative errors of the method of the present invention at different concentrations. Detailed Implementation

[0028] Figure 5-12 The following description illustrates optional embodiments of the invention to teach those skilled in the art how to implement and reproduce the invention. Some conventional aspects have been simplified or omitted to explain the technical solutions of the invention. Those skilled in the art should understand that variations or substitutions derived from these embodiments will be within the scope of the invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the following optional embodiments, but is defined only by the claims and their equivalents.

[0029] Example 1:

[0030] Figure 5 A flowchart illustrating a gas detection method based on absorption spectroscopy according to an embodiment of the present invention is shown, such as... Figure 5 As shown, the gas detection method based on absorption spectroscopy technology includes the following steps:

[0031] (A1) Various concentrations of standard gases are introduced into a gas cell, and the pressure inside the gas cell is adjusted to obtain the concentration values ​​C of the various concentrations of standard gases at different pressures. 仪 ,like Figure 6 As shown;

[0032] (A2) For the same standard gas By fitting the pressure P of the standard gas, the pressure fitting parameters P′ and C corresponding to the standard gas are obtained. 标 It is the nominal concentration of the standard gas;

[0033] (A3) Nominal concentration of standard gas C 标 The pressure fitting parameter P′ is processed to obtain the pressure fitting parameter P′ and the nominal concentration C. 标 The correspondence between them, such as Figure 7 As shown, and store;

[0034] (A4) Introduce the sample gas into the gas cell and obtain the sample gas pressure P in the gas cell. 测 The instrument concentration C of the sample gas was obtained using absorption spectroscopy. 测 To obtain the concentration P0 is atmospheric pressure;

[0035] (A5) Substitute concentration C into the aforementioned correspondence to obtain P corresponding to concentration C. 实 Thus, the sample gas concentration is obtained.

[0036] To reduce the difficulty of fitting, further, in step (A2), the fitting method is as follows:

[0037] Thus, the parameters k and P′ are obtained.

[0038] To obtain the correspondence, in step (A2), polynomial interpolation is used to derive the correspondence.

[0039] Example 2:

[0040] An application example of the gas detection method based on absorption spectroscopy technology according to Embodiment 1 of the present invention for carbon monoxide detection.

[0041] In this application example, such as Figure 5 As shown, the gas detection method based on absorption spectroscopy technology includes the following steps:

[0042] (A1) Carbon monoxide standard gases with concentrations of 10 ppm, 25 ppm, 50 ppm, and 80 ppm were introduced into a gas cell, and the pressure in the gas cell was adjusted so that each concentration of standard gas corresponded to a standard gas pressure, with the pressure increasing from 50 kPa to 130 kPa in increments of 10 kPa. The concentration value C of each concentration of standard gas at different pressures was obtained using NDIR technology. 仪 ;like Figure 6 As shown, The relationship between the standard gas pressure P and the standard gas pressure is basically linear.

[0043] (A2) For the same standard gas Linear fitting was performed with the standard gas pressure P. Thus, the parameters k and the pressure fitting parameters P′ and C corresponding to the standard gas are obtained. 标 It is the nominal concentration of the standard gas;

[0044] Standard gas concentration (ppm) 10 25 50 80 Pressure fitting parameters (kPa) 30.98 -7 -15.75 -24.78

[0045] (A3) Nominal concentration of standard gas C 标 Polynomial interpolation is performed on the corresponding pressure fitting parameter P′ to obtain the pressure fitting parameter P′ and the nominal concentration C. 标 The correspondence between them, such as Figure 7 As shown, and store;

[0046] (A4) Introduce the sample gas into the gas cell and obtain the sample gas pressure P in the gas cell. 测 The instrument concentration C of the sample gas was obtained using NDIR technology. 测 To obtain the concentration P0 is atmospheric pressure;

[0047] (A5) Substitute concentration C into the aforementioned correspondence to obtain P corresponding to concentration C. 实 Thus, the sample gas concentration is obtained.

[0048] Verification example:

[0049] According to Embodiment 2 of the present invention, a gas detection method based on absorption spectroscopy is used to detect carbon monoxide standard gases with concentrations of 10 ppm, 25 ppm, 50 ppm, and 80 ppm.

[0050] Obtained Please see the appendix for the correspondence between pressure and pressure. Figure 8-11 As can be seen from the figure, compared with the three compensation methods in the prior art, the detection method of the present invention is closer to the nominal concentration of the standard gas over a large concentration range, with a smaller relative error. Figure 12 As shown.

Claims

1. A gas detection method based on absorption spectroscopy, the gas detection method based on absorption spectroscopy comprising the following steps: (A1) Various concentration standard gases were introduced into a gas cell, and the pressure inside the gas cell was adjusted to obtain the concentration values ​​C of the various concentration standard gases at different pressures. 仪 ; (A2) C for the same standard gas 仪 / C 标 By fitting the pressure P of the standard gas, the pressure fitting parameters Pˊ and C corresponding to the standard gas are obtained. 标 It is the nominal concentration of the standard gas; (A3) Nominal concentration C of the standard gas 标 The pressure fitting parameter Pˊ is processed to obtain the pressure fitting parameter Pˊ and the nominal concentration C. 标 Establish and store the correspondence between them; (A4) The sample gas is introduced into the gas cell to obtain the sample gas pressure P in the gas cell. 测 The instrument concentration C of the sample gas was obtained using absorption spectroscopy. 测 The concentration C is obtained as C = P0·C 测 / P 测 P0 is atmospheric pressure; the concentration range of the sample gas is 10ppm-80ppm; (A5) Substitute concentration C into the aforementioned correspondence to obtain P corresponding to concentration C. 实 Thus, the sample gas concentration C is obtained. 补 = (P0+P 实 )·C 测 / ( P 测 + P 实 ).

2. The gas detection method based on absorption spectroscopy technology according to claim 1, characterized in that, In step (A2), the fitting method is as follows: C 仪 / C 标 =k·(P- Pˊ), thus obtaining the parameters k and Pˊ.

3. The gas detection method based on absorption spectroscopy technology according to claim 1, characterized in that, In step (A2), the correspondence is obtained by using polynomial interpolation.

4. The gas detection method based on absorption spectroscopy technology according to claim 1, characterized in that, The absorption spectroscopy technique is NDIR.

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