Method and system for detecting multiple gas concentrations with cross-interference elimination

Abstract

The application provides a method and system for detecting concentrations of multiple gases to eliminate cross interference. The method comprises the following steps: determining a target absorption spectrum interval, a target absorption spectrum, a target detection wavelength of each to-be-detected gas, and an interference gas, performing spectrum detection on the interference gas to obtain an absorption spectrum of the interference gas; determining a relative absorbance coefficient according to the absorption spectrum; performing spectrum detection on a mixed gas of all to-be-detected gases to obtain an absorption spectrum of the mixed gas; then obtaining absorbance of a to-be-detected gas with an independent peak; calculating actual absorbance of the to-be-detected gas according to the relative absorbance coefficient and the absorbance of the to-be-detected gas with the independent peak; and calculating the concentration of the to-be-detected gas in the mixed gas. The method provided by the application can detect the concentrations of multiple to-be-detected gases simultaneously, does not need to set an additional hardware device, reduces the cost, does not have the problems of reducing gas absorption intensity and detection lower limit, and is more conducive to miniaturization and micro-miniaturization of a detection device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spectral detection technology, and particularly relates to a method and system for detecting concentrations of multiple gases by eliminating cross interference. BACKGROUND

[0002] As a commonly used gas detection method, tunable diode laser absorption spectroscopy (TDLAS) has been widely applied in industries such as mineral development, chemical industry, environmental monitoring, and has the advantages of high sensitivity, good stability, high detection accuracy, long service life, etc.

[0003] For application scenarios such as coal spontaneous combustion early warning and natural gas leakage detection, simultaneous detection of multiple-component gases is required. Coal spontaneous combustion early warning can produce different marker gases according to different stages of coal spontaneous combustion, so the coal combustion state can be judged by accurately detecting multiple different marker gases, and early warning can be achieved.

[0004] For natural gas leakage detection, methane and ethane gases need to be detected simultaneously to exclude the interference of biogas. The commonly used methods for simultaneous detection of multiple gases include reducing the pressure of the gas chamber and using multiple lasers to detect each gas. The multiple-laser detection method usually requires multiple gas chambers to be used together, which is high in use cost and not conducive to product miniaturization. The method of reducing the pressure of the gas chamber requires an additional vacuum pump, which is also high in use cost. SUMMARY

[0005] The present application provides a method and system for detecting concentrations of multiple gases by eliminating cross interference, to solve the technical problem of high use cost and poor product miniaturization in the process of simultaneous detection of multiple gas components.

[0006] In a first aspect, the present application provides a method for detecting concentrations of multiple gases while eliminating cross interference, comprising: determining a target absorption spectrum interval corresponding to a to-be-detected gas, determining a target absorption spectrum according to the target absorption spectrum interval, and determining a target detection wavelength of each to-be-detected gas, wherein the target detection wavelength is a wavelength corresponding to a highest absorption peak of the to-be-detected gas in the target absorption spectrum, and the target absorption spectrum comprises an absorption spectrum of each to-be-detected gas in the target absorption spectrum interval; determining an interference gas of each to-be-detected gas according to the target detection wavelength of each to-be-detected gas, and performing spectral detection on each interference gas respectively to obtain an absorption spectrum of each interference gas; determining a relative absorbance coefficient of each interference gas at the target detection wavelength of other to-be-detected gases relative to the target detection wavelength of the interference gas itself according to the absorption spectrum of each interference gas; performing spectral detection on a mixed gas of all to-be-detected gases to obtain an absorption spectrum of the mixed gas; obtaining an absorbance of the to-be-detected gas having an independent peak according to the absorption spectrum of the mixed gas; calculating an actual absorbance of each to-be-detected gas at the target detection wavelength in the mixed gas according to the relative absorbance coefficient of each interference gas and the absorbance of the to-be-detected gas having the independent peak; and calculating a concentration of each to-be-detected gas in the mixed gas according to the actual absorbance of each to-be-detected gas at the target detection wavelength.

[0007] In some embodiments of the present application, the determination of the interference gas of each to-be-detected gas according to the target detection wavelength of each to-be-detected gas comprises: determining other to-be-detected gases having a non-zero absorbance at the target detection wavelength of the to-be-detected gas, and determining the to-be-detected gases having the non-zero absorbance as the interference gas of the to-be-detected gas.

[0008] In some embodiments of the present application, the determination of the relative absorbance coefficient of each interference gas at the target detection wavelength of other to-be-detected gases relative to the target detection wavelength of the interference gas itself according to the absorption spectrum of each interference gas comprises: determining a first absorbance of each interference gas at the target detection wavelength of the interference gas; determining a second absorbance of each interference gas at the target detection wavelength of other to-be-detected gases; and for each interference gas, taking a ratio of the second absorbance to the first absorbance as the relative absorbance coefficient of the interference gas.

[0009] In some embodiments of the present application, the method comprises: determining the independent peak in the target absorption spectrum; determining the absorbance of the target gas with the independent peak in the absorption spectrum of the mixed gas according to the independent peak; wherein the absorbance of the remaining target gases at the target detection wavelength corresponding to the independent peak is zero.

[0010] In some embodiments of the present application, the method comprises: establishing an absorbance equation group for each target gas in the mixed gas at the target detection wavelength; and bringing the relative absorbance coefficient of each interfering gas and the absorbance of the target gas with the independent peak into the absorbance equation group to obtain the actual absorbance of each target gas in the mixed gas at the target detection wavelength.

[0011] In some embodiments of the present application, the absorbance equation group is:

[0012]

[0013] wherein a 11 , a 12 , …, a 1n , a 21 , a 22 , a 2n , a n1 , a n2 , a nn is the relative absorbance coefficient of the target gas at the target detection wavelength; γ1, γ2, …, γ n is the actual absorbance of the target gas at the respective target detection wavelength; A1, A2, …, An n is the superposition sum of the absorbance of the mixed gas corresponding to the target detection wavelength; and n is the number of target gases.

[0014] In some embodiments of the present application, the method comprises: determining the maximum wavelength and the minimum wavelength in the plurality of target gases; and generating the target absorption spectrum interval in the wavelength range covering the maximum wavelength and the minimum wavelength.

[0015] In some embodiments of the present application, the calculating the concentration of each of the to-be-detected gases in the mixed gas according to the actual absorbance of each of the to-be-detected gases at the target detection wavelength comprises: obtaining a calibration function by using a standard gas detection method according to the relationship between gas absorbance and gas concentration; and bringing the actual absorbance of the mixed gas into the calibration function to obtain the concentration of each of the to-be-detected gases in the mixed gas.

[0016] The second aspect of the present application provides a detection system for multiple gas concentrations with cross interference eliminated, comprising: a signal generator configured to output a modulation signal; a laser connected to the signal generator and configured to receive the modulation signal and output a first optical signal according to the modulation signal, wherein the output wavelength range of the first optical signal can cover a target absorption spectral interval; a photodetection module configured to receive a second optical signal and convert the second optical signal into an electrical signal, wherein the second optical signal is an optical signal with to-be-detected gas concentration information generated after the first optical signal is absorbed by a gas; a data acquisition module connected to the photodetection module and configured to receive the electrical signal and convert the electrical signal into a digital signal; and an upper computer connected to the data acquisition module and configured to receive the digital signal, calculate a relative absorbance coefficient of each of the interference gases at a target detection wavelength of other to-be-detected gases relative to a target detection wavelength of the interference gas itself based on the digital signal, and calculate an actual absorbance of each of the to-be-detected gases in a mixed gas at the target detection wavelength according to the relative absorbance coefficient of each of the interference gases and the absorbance of the to-be-detected gas with an independent peak; the upper computer is further configured to calculate the concentration of each of the to-be-detected gases in the mixed gas according to the actual absorbance of each of the to-be-detected gases at the target detection wavelength.

[0017] In some embodiments of the present application, the detection system further comprises a laser controller and a collimating lens; the laser controller is connected to the signal generator and the laser respectively and configured to receive the modulation signal and control the wavelength of the light emitted by the laser according to the modulation signal to generate the optical signal; and the collimating lens is arranged on the light path of the first optical signal and configured to collimate the first optical signal.

[0018] The detection method and system for multiple gas concentrations with cross interference eliminated provided by the present application can simultaneously detect multiple to-be-detected gases in a mixed gas without the need for one-by-one detection, and can realize the simultaneous detection of multiple gas concentrations by eliminating the cross interference between different to-be-detected gases. On the premise of ensuring detection accuracy, no additional hardware devices need to be set, thereby reducing the detection cost. In addition, there is no problem of reducing the gas absorption intensity and the detection lower limit, which is more conducive to the miniaturization and microfabrication of the detection device. Attached Figure Description

[0019] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic flowchart illustrating a method for detecting the concentrations of multiple gases to eliminate cross-interference, provided in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram illustrating the cross-interference of the absorption spectra of methane, ethane, and water in the embodiments of this application.

[0022] Figure 3 The absorption spectrum of ethane in the embodiments of this application is shown.

[0023] Figure 4 The absorption spectrum of water in the embodiments of this application;

[0024] Figure 5 This is a schematic diagram of the process for calculating the relative absorbance coefficient in an embodiment of this application;

[0025] Figure 6 The absorption spectrum of the mixed gas provided in the embodiments of this application;

[0026] Figure 7 Examples of embodiments in this application Figure 2 and Figure 6 A schematic diagram of the combination;

[0027] Figure 8 This is a schematic diagram of the calibration function of ethane provided in the embodiments of this application;

[0028] Figure 9 This is a schematic diagram of the calibration function for methane provided in the embodiments of this application;

[0029] Figure 10 A schematic diagram of the calibration function for water provided in an embodiment of this application;

[0030] Figure 11 This is a schematic diagram of a multi-gas concentration detection system that eliminates cross-interference, provided in an embodiment of this application.

[0031] Illustration:

[0032] 10-Signal generator; 20-Laser controller; 30-Laser; 40-Collimating lens; 50-Gas chamber; 60-Photoelectric detection module; 70-Data acquisition module; 80-Host computer. Detailed Implementation

[0033] The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments of the present application, other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0034] Hereinafter, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0035] In addition, in the present application, the orientation terms such as "upper", "lower", "inner", "outer", and the like are defined with respect to the orientation of the components shown in the drawings, and it should be understood that these directional terms are relative concepts, which are used for relative description and clarification, and can be changed accordingly according to the change of the orientation of the components placed in the drawings.

[0036] In the industries of mineral development, chemical industry, environmental detection, etc., early warning of dangerous gas is the key direction in production and development. For example, coal spontaneous combustion warning will usually produce different marker gases according to different stages of coal spontaneous combustion, so the combustion state of coal can be determined by detecting a plurality of different marker gases, and then early warning can be made. For example, the detection of natural gas leakage usually needs to detect methane and ethane to exclude the interference of biogas. At present, the commonly used method for simultaneous detection of multiple gases mainly includes the method of using a plurality of laser arrays to detect each gas respectively and the method of reducing the pressure of the gas chamber to reduce the broadening of the absorption peaks of different gases, so as to reduce the cross interference between the absorption spectral lines of multiple gases.

[0037] The method of using a plurality of laser arrays needs a plurality of lasers, each laser usually only realizes the detection of one gas, so when selecting the gas absorption spectral line, usually only one gas absorption spectral line is selected, and the selected spectral line is usually not disturbed or slightly disturbed by other gases. Therefore, the freedom degree of spectral selection of the method of using a plurality of laser arrays is large, the wavelengths of the selected absorption peaks of different gases are usually quite different, and the cross interference problem between multiple gases almost does not need to be considered. However, the obvious disadvantage of this method is that a plurality of lasers are needed, and sometimes even a plurality of gas chambers are needed. It needs high cost and the volume of the detection equipment is large, which is usually not conducive to the miniaturization of the detection equipment.

[0038] The method for reducing the pressure of the gas chamber mainly utilizes the fact that the absorption peak of the gas will be reduced in width under low pressure conditions, thereby reducing the problem of cross interference of multiple gas absorption peaks. However, the low pressure conditions will also reduce the absorption intensity of the gas, thereby reducing the detection precision and detection limit. The method for reducing the pressure of the gas chamber is usually achieved by using a vacuum pump to realize low pressure conditions, and therefore, an additional vacuum pump device and low pressure control circuit are required. Although this method does not require a large number of lasers to be arranged compared with the multi-laser array method, the additional vacuum pump and pressure control circuit still result in a high cost and a large size of the detection device.

[0039] To solve the technical problems of high detection cost and large size caused by the above two methods, the application provides a detection method for multiple gas concentrations to eliminate cross interference. The method can realize the simultaneous detection of the concentrations of multiple gases in a mixed gas, effectively reduce the detection cost, and facilitate the miniaturization and micro-miniaturization of the detection device.

[0040] To facilitate the technical solutions of the application, some concepts involved in the application are first described.

[0041] Spectrum, full name optical spectrum, is the pattern of monochromatic light dispersed by a dispersion system (such as a prism, grating) after the dispersion of a complex color light, and the monochromatic light is arranged in order according to the wavelength (or frequency).

[0042] Absorbance: the ratio of the incident light intensity before the light passes through a solution or a substance to the transmitted light intensity after the light passes through a solution or a certain substance. The factors affecting it include solvent, concentration, temperature, etc.

[0043] Wave number: a frequency unit in atomic, molecular and nuclear spectroscopy. The symbol is σ or v, which is equal to the real frequency divided by the speed of light, that is, the reciprocal of the wavelength (λ), and the unit is cm -1 .

[0044] Figure 1 A flowchart of a detection method for multiple gas concentrations to eliminate cross interference provided by an embodiment of the application.

[0045] Referring to Figure 1 The detection method for multiple gas concentrations to eliminate cross interference provided by an embodiment of the application is realized by the following steps S100-S700:

[0046] Step S100: determining the target absorption spectrum interval corresponding to the to-be-detected gas, determining the target absorption spectrum according to the target absorption spectrum interval, and determining the target detection wavelength of each to-be-detected gas.

[0047] The target detection wavelength is the wavelength corresponding to the peak value of the highest absorption peak of the to-be-detected gas in the target absorption spectrum, and the target absorption spectrum includes the absorption spectrum of each to-be-detected gas in the target absorption spectrum range.

[0048] In step S100, the target absorption spectrum range contains the wavelength range of the plurality of to-be-detected gases. The minimum wavelength of the target absorption spectrum range is less than or equal to the minimum wavelength of the plurality of to-be-detected gases, and the maximum wavelength of the target absorption spectrum range is greater than or equal to the maximum wavelength of the plurality of to-be-detected gases.

[0049] Specifically, the target absorption spectrum is determined according to the target absorption spectrum range, and the target absorption spectrum includes the absorption spectrum of each to-be-detected gas. It can be understood that the absorption spectrum of each to-be-detected gas is generated in the target absorption spectrum range, and the peak value of the absorption peak of each to-be-detected gas can be correspondingly queried.

[0050] In the target absorption spectrum, the peak value of the highest absorption peak is the maximum value of the to-be-detected gas absorbance. The to-be-detected gas may have one absorption peak or multiple absorption peaks in the target absorption spectrum. When the to-be-detected gas has multiple absorption peaks, the absorption peak with the maximum absorbance is the highest absorption peak. In this way, each to-be-detected gas has one highest absorption peak, and each to-be-detected gas corresponds to one target detection wavelength.

[0051] It is worth noting that the detection method of the plurality of gas concentrations for eliminating cross interference provided in the embodiment of the present application is performed on the premise that the types of to-be-detected gases are known.

[0052] Figure 2 The absorption spectrum cross interference diagram of the three gases of methane, ethane, and water in the embodiment of the present application is shown.

[0053] Referring to Figure 2 Taking the existence of methane CH4, ethane C2H6, and water H2O in the mixed gas as an example, the concentration detection method in the embodiment of the present application is explained and described. The water is gaseous water, the methane and the ethane are detected under the conditions of 25 cm effective optical path and normal temperature and pressure, and the water is detected under the conditions of 10 cm effective optical path and normal temperature and pressure.

[0054] It should be emphasized that the detection method provided in the embodiment of the present application is not limited to detecting the concentrations of three gases at the same time, but can also detect the concentrations of more or fewer types of gases at the same time. Figure 2 The types and quantities of gases in the embodiment of the present application are only exemplary.

[0055] Specifically, Figure 2 The target absorption spectrum range in the embodiment of the present application corresponds to a wave number range of [2985 cm -1 , 2992 cm -1The wavelength range of any one of methane, ethane, and water is within the target absorption spectrum interval.

[0056] The ethane has two absorption peaks, N1 at wave number 2986.68 cm -1 and N5 at wave number 2990.00 cm -1 The ethane has the highest absorption peak at wave number 2986.68 cm -1 , i.e., N1, and the corresponding wavelength at wave number 2986.68 cm -1 is the target detection wavelength of ethane.

[0057] The water has two absorption peaks, N2 at wave number 2987.53 cm -1 and N3 at wave number 2988.50 cm -1 The water has the highest absorption peak at wave number 2987.53 cm -1 , i.e., N2, and the corresponding wavelength at wave number 2987.53 cm -1 is the target detection wavelength of water.

[0058] The methane has one absorption peak, N4, which is the highest absorption peak. The corresponding target detection wavelength of the highest absorption peak of methane is at wave number 2988.80 cm -1 .

[0059] It is worth noting that, Figure 2 in the target absorption spectrum interval, the wave number is used instead of the wavelength. This is mainly because the number of digits after the decimal point is large when the wavelength is used. The wave number is used in the following embodiments of the present application.

[0060] Step S200: Determine the interference gas of each to-be-detected gas according to the target detection wavelength of each to-be-detected gas, and perform spectral detection on each interference gas to obtain the absorption spectrum of each interference gas.

[0061] The to-be-detected gas is multiple, and the number of target detection wavelengths is the same as the number of to-be-detected gases. Since the spectral graphs of multiple gases in the mixed gas are crossed, the highest absorption peak of any to-be-detected gas is interfered by the remaining to-be-detected gases, and thus the absorbance of the to-be-detected gas with the highest absorption peak is interfered. Therefore, at the target detection wavelength, it is necessary to determine whether there is an interference gas, so as to eliminate the cross interference and improve the detection accuracy.

[0062] Specifically, the judgment method of the interference gas is that the other to-be-detected gas with a non-zero absorbance at the target detection wavelength of the to-be-detected gas is the interference gas of the to-be-detected gas.

[0063] See also Figure 2 wavenumber 2986.68cm -1 The corresponding wavelength is the target detection wavelength for ethane. The wavenumber for ethane is 2986.68 cm⁻¹. -1 At this wavelength, the absorbance of both water and methane is zero. Therefore, at the target detection wavelength for ethane, there are no interfering gases associated with ethane.

[0064] Wavenumber 2987.53cm -1 The corresponding wavelength is the target detection wavelength for water. At a wavenumber of 2987.53 cm⁻¹, this is the target detection wavelength for water. -1 At the specified wavelength, ethane has a non-zero absorbance, while methane has a zero absorbance. Therefore, at the target detection wavelength for water, the interfering gas is ethane.

[0065] Wavenumber 2988.80cm -1 The corresponding wavelength is the target detection wavelength for methane. The methane wavenumber is 2988.80 cm⁻¹. -1 At the target detection wavelength for methane, the absorbance of both ethane and water is not zero. Therefore, at the target detection wavelength for methane, the interfering gases are ethane and water.

[0066] Figure 3 The absorption spectrum of ethane in the embodiments of this application is shown.

[0067] Figure 4 This is the absorption spectrum of water in the embodiments of this application.

[0068] See Figure 3 and Figure 4 After identifying the interfering gases, ethane and water were subjected to spectral detection using a single-laser TDLAS direct absorption detection technique, yielding the absorption spectra of ethane and water, respectively.

[0069] Step S300: Based on the absorption spectrum of each interfering gas, determine the relative absorbance coefficient of each interfering gas at the target detection wavelength of other gases relative to the target detection wavelength of the interfering gas itself.

[0070] Specifically, the absorbance of the interfering gas at the target detection wavelength is the peak value of the highest absorption peak.

[0071] Figure 5 This is a schematic diagram of the process for calculating the relative absorbance coefficient in an embodiment of this application.

[0072] See Figure 5 In this embodiment, the method for calculating the relative absorbance coefficient is implemented by the following steps S301-S303:

[0073] Step S301: Determine the first absorbance of each interfering gas at its own target detection wavelength.

[0074] wherein the first absorbance is the highest absorbance peak of the interfering gas.

[0075] Step S302: determining the second absorbance of each interfering gas at the target detection wavelength of other to-be-detected gases.

[0076] Specifically, the second absorbance is the corresponding absorbance of the interfering gas at the target detection wavelength of other to-be-detected gases.

[0077] For example, continuing to refer to Figure 3 , the first absorbance of ethane is at the wave number 2986.68 cm -1 , the second absorbance of ethane is at the wave number 2987.53 cm -1 , and the second absorbance of ethane is at the wave number 2988.80 cm -1 .

[0078] For example, continuing to refer to Figure 4 , the first absorbance of water is at the wave number 2987.53 cm -1 , and the second absorbance of water is at the wave number 2988.80 cm -1 .

[0079] wherein the absorbance coefficients of the same interfering gas at different target detection wavelengths can be the same or different.

[0080] Step S303: for each interfering gas, taking the ratio of the second absorbance to the first absorbance as the relative absorbance coefficient of the interfering gas.

[0081] Specifically, the relative absorbance coefficient of the interfering gas at different target detection wavelengths is calculated according to the second absorbance and the first absorbance at different target detection wavelengths.

[0082] For example, continuing to refer to Figure 3 . The second absorbance of ethane at the wave number 2987.53 cm -1 and 2988.80 cm -1 is respectively taken as the ratio of the first absorbance, and the relative absorbance coefficient of ethane at the wave number 2987.53 cm -1 is 3.19%, and the relative absorbance coefficient of ethane at the wave number 2988.80 cm -1 is 2.77%.

[0083] For example, continuing to refer to Figure 4 . The second absorbance of water at the wave number 2988.80 cm -1 is taken as the ratio of the first absorbance at the wave number 2987.53 cm -1The relative absorbance coefficient of water at the wave number 2988.80 cm -1 is 4.96%.

[0084] Step S400: Perform spectrum detection on the mixed gas of all the to-be-detected gases to obtain an absorption spectrum of the mixed gas.

[0085] Figure 6 The absorption spectrum of the mixed gas provided in the embodiments of the present application.

[0086] Referring to Figure 6 , the mixed gas is detected by using the single-laser TDLAS direct absorption technology to obtain the absorption spectrum of the mixed gas.

[0087] Step S500: Obtain the absorbance of the to-be-detected gas with the independent peak according to the absorption spectrum of the mixed gas.

[0088] At the target detection wavelength corresponding to the independent peak, the absorbance of the rest of the to-be-detected gases is zero. That is, the independent peak is not interfered by the rest of the to-be-detected gases, and there is no interfering gas at the independent peak.

[0089] Step S500 is implemented by steps S501-S502:

[0090] Step S501: Determine the independent peak in the target absorption spectrum.

[0091] For example, continuing to refer to Figure 2 , it can be seen from the target absorption spectrum that the absorbance of methane and water at the wave number 2986.68 cm -1 of ethane is zero. It can also be understood that, at the wave number 2986.68 cm -1 of ethane, that is, at the target detection wavelength of ethane, methane and water do not interfere with ethane, and then N1 is the independent peak.

[0092] Step S502: In the absorption spectrum of the mixed gas, determine the absorbance of the to-be-detected gas with the independent peak according to the independent peak.

[0093] For example, after judging that N1 is the independent peak, continuing to refer to Figure 6 , the peak value of the independent peak is the absorbance of the ethane gas.

[0094] Step S600: Calculate the actual absorbance of each to-be-detected gas in the mixed gas at the target detection wavelength according to the relative absorbance coefficient of each interfering gas and the absorbance of the to-be-detected gas with the independent peak.

[0095] The relative absorbance coefficient of each interfering gas is obtained in step S303. The absorbance of the analyte gas with an independent peak is obtained in step S502.

[0096] Figure 7 Examples of embodiments in this application Figure 2 and Figure 6 A schematic diagram of the combination.

[0097] See Figure 7 It is known that when interfering gases are present at the target detection wavelength in a gas mixture, the sum of absorbance is greater than the absorbance of the analyte gas whose absorption peak is located at that target detection wavelength in the target detection spectrum. This is also a result of cross-interference. In this case, the sum of absorbance cannot be used as the basis for subsequent calculation of gas concentration; it is necessary to calculate the actual absorbance of each analyte gas in the gas mixture.

[0098] Specifically, step S600 is implemented by the following steps S601-S602:

[0099] Step S601: Establish a set of absorbance equations for each gas to be tested in the mixed gas at the target detection wavelength.

[0100] Step S602: Substitute the relative absorbance coefficient of each interfering gas and the absorbance of the gas to be tested with an independent peak into the absorbance equation set to obtain the actual absorbance of each gas to be tested in the mixed gas.

[0101] Specifically, the absorbance equations are as follows:

[0102]

[0103] Among them, a 11 a 12 …a 1n a 21 a 22 …a 2n a n1 a n2 …a nn The relative absorbance coefficients of each analyte gas at the target detection wavelength; γ1, γ2…γ n A1, A2…A2 represent the actual absorbance of the gas to be tested at their respective target detection wavelengths. n is the sum of absorbance at the target detection wavelength in the absorption spectrum of the mixed gas, where n is the number of gases to be measured.

[0104] It is worth noting that the interfering gas can be any type of gas being tested.

[0105] For example, let's continue with the case where the gas to be measured is methane, ethane, and water. In this case, n is 3, and the above absorbance equations are:

[0106]

[0107] wherein γ1 is the actual absorbance of ethane, γ2 is the actual absorbance of methane, and γ3 is the actual absorbance of water. Since γ1 is ethane, and ethane has an independent peak at 2986.68 cm-1 which is not interfered by other gases, the relative absorbance coefficients of ethane at the target detection wavelengths of methane and water are both 0, i.e. a -1 = 0, a 12 = 0, and a 13 = 1. Thus, γ1 = A1. A1 is the superimposed sum of absorbance at wave number 2986.68 cm-1 in the detection spectrum of the mixed gas. Therefore, the actual absorbance of ethane with an independent peak is equal to the superimposed sum of absorbance at the target detection wavelength, i.e. the peak value of the independent peak. 11 -1 = 1. Thus, γ1 = A1. A1 is the superimposed sum of absorbance at wave number 2986.68 cm-1 in the detection spectrum of the mixed gas. Therefore, the actual absorbance of ethane with an independent peak is equal to the superimposed sum of absorbance at the target detection wavelength, i.e. the peak value of the independent peak.

[0108] It is worth noting that the above example is an independent peak. In actual detection process, the number of independent peaks can be one or more.

[0109] Specifically, according to the relative absorbance coefficients obtained in the above steps and the peak value of the independent peak, the following absorbance equations are obtained at wave numbers 2986.68 cm-1, 2987.53 cm-1 and 2988.8 cm-1: -1 -1 -1

[0110]

[0111] By the above equations, γ2 = 0.00365084465 and γ3 = 0.0155570540553 can be solved; i.e. the absorbance of ethane at wave number 2986.68 cm-1 is 0.0199262, the absorbance of water at wave number 2987.53 cm-1 is 0.00365084465, and the absorbance of methane at wave number 2988.8 cm-1 is 0.0155570540553. -1 -1 -1

[0112] Step S700: according to the actual absorbance of each kind of gas to be detected at the target detection wavelength, the concentration of each kind of gas to be detected in the mixed gas is calculated.

[0113] Specifically, step S700 is realized by the following steps S701-S702:

[0114] Step S701: according to the relationship between gas absorbance and gas concentration, a calibration function is obtained by using standard gas detection method. ​​​​​​​

[0115] Specifically, the standard gas is a term in the gas industry, which is a measurement standard with uniform concentration, good stability and accurate measurement value. The method for detecting the standard gas is a method for detecting by using the standard gas.

[0116] Step S702: The actual absorbance in the mixed gas is brought into the calibration function to obtain the concentration of each to-be-detected gas in the mixed gas.

[0117] Specifically, the absorbance of the gas is linearly related to the concentration of the gas.

[0118] Figure 8 The calibration function diagram of ethane provided for the embodiment of the present application is shown.

[0119] Figure 9 The calibration function diagram of methane provided for the embodiment of the present application is shown.

[0120] Figure 10 The calibration function diagram of water provided for the embodiment of the present application is shown.

[0121] Referring to Figure 8 , the calibration function of ethane is y=1007*x-0.0007236. Wherein, x is the actual absorbance, and y is the gas concentration. R 2 is the determination coefficient, which represents the proportion of x explaining the change of the response variable with y. R 2 The greater, the greater the variation explained by the calibration function, that is, the more accurate the calibration function reflects the relationship between the absorbance and the concentration.

[0122] Referring to Figure 9 , the calibration function of methane is y=2570*x-0.0003316. Wherein, x is the actual absorbance, and y is the gas concentration. R 2 is the determination coefficient.

[0123] Referring to Figure 10 , the calibration function of water is y=3082000*x-1100. Wherein, x is the actual absorbance, and y is the gas concentration. R 2 is the determination coefficient.

[0124] The actual absorbance coefficient calculated in step S602 is brought into the above calibration function to calculate the concentrations of the three gases. Finally, the concentration of ethane in the mixed gas is 20.06 ppm (parts per million, ppm), the concentration of methane is about 39.98 ppm, and the concentration of water is about 1.01519%.

[0125] Therefore, the method for detecting multiple gases by eliminating cross interference provided by the embodiment of the application can detect multiple to-be-detected gases in the mixed gas simultaneously without detecting them one by one. By eliminating the cross interference between different to-be-detected gases, the simultaneous detection of multiple gas concentrations is realized. Without the need of setting additional hardware devices, the detection cost is reduced under the premise of ensuring the detection accuracy. In addition, there is no problem of reducing the gas absorption intensity and the detection lower limit, which is more conducive to the miniaturization and micro-miniaturization of the detection device.

[0126] Corresponding to the foregoing embodiment of the method for detecting multiple gas concentrations by eliminating cross interference, the application further provides an embodiment of a system for detecting multiple gas concentrations by eliminating cross interference.

[0127] Figure 11 A structural schematic diagram of a system for detecting multiple gas concentrations by eliminating cross interference provided by the embodiment of the application.

[0128] Referring to Figure 11 , the detection system comprises a signal generator 10, a laser 30, a photoelectric detection module 60, a data acquisition module 70, an upper computer 80, a laser controller 20, and a collimating lens 40.

[0129] The signal generator 10 is configured to send a modulation signal.

[0130] The laser 30 is connected to the signal generator 10 and is configured to receive the modulation signal and output a first optical signal according to the modulation signal. The wavelength range of the first optical signal can cover the target absorption spectrum interval.

[0131] The laser controller 20 is connected to the signal generator 10 and the laser 30, and is configured to receive the modulation signal and control the wavelength of the light emitted by the laser 30 according to the modulation signal to generate the first optical signal.

[0132] The collimating lens 40 is arranged on the light path of the first optical signal and is configured to collimate the first optical signal.

[0133] The photoelectric detection module 60 is distributed in the to-be-detected gas chamber 50 and is configured to receive a second optical signal and convert the second optical signal into an electrical signal. The second optical signal is an optical signal with to-be-detected gas concentration information generated after the first optical signal is absorbed by the gas.

[0134] The data acquisition module 70 is connected to the photoelectric detection module 60 and is configured to receive the electrical signal and convert the electrical signal into a digital signal.

[0135] The host computer 80, connected with the data acquisition module 70, is configured to receive the digital signal, calculate the relative absorbance coefficient of each interfering gas at the target detection wavelength of other to-be-detected gases based on the digital signal, and calculate the actual absorbance of each to-be-detected gas at the target detection wavelength in the mixed gas according to the relative absorbance coefficient of each interfering gas and the absorbance of the to-be-detected gas with an independent peak.

[0136] The host computer 80 is further configured to calculate the concentration of each to-be-detected gas in the mixed gas according to the actual absorbance of each to-be-detected gas at the target detection wavelength.

[0137] Specifically, the modulated signal generated by the signal generator 10 is input to the laser controller 20, and then the laser controller 20 tunes the laser 30, so that the output wavelength range of the laser 30 can cover the target absorption spectrum interval. Then, the light signal output by the laser 30 is collimated by the collimating lens 40 and then enters the gas chamber 50. The collimating lens 40 is arranged on the light path of the first light signal. The gas chamber 50 is filled with to-be-detected gas. At this time, the first light signal contacts the gas in the gas chamber 50 and is absorbed by the gas in the gas chamber 50 to generate a second light signal with to-be-detected gas concentration information. Then, the photoelectric detection module 60 converts the detected second light signal with to-be-detected gas concentration information into an electric signal and performs amplification processing. At this time, the electric signal carries to-be-detected gas concentration information. Finally, the data acquisition module 70 uploads data to the host computer 80 for calculation of the relative absorbance coefficient, the actual absorbance, and the to-be-detected gas concentration.

[0138] The host computer 80 can be a computer.

[0139] Through the calculation of the relative absorbance coefficient by the host computer 80, the actual absorbance of multiple gases in the mixed gas can be obtained, so that the concentrations of the multiple gases in the mixed gas can be further calculated simultaneously. On the premise of ensuring the detection accuracy, no additional hardware device needs to be arranged, and the detection cost is reduced. In addition, there is no problem of reducing the gas absorption intensity and the detection lower limit, which is more conducive to the miniaturization and microfabrication of the detection device.

[0140] It should be noted that other embodiments of the application will occur to those skilled in the art having the benefit of the present disclosure. The application is intended to cover any variations, uses or adaptive changes of the application following, in general, the principles of the application and including such as are within its generic concepts. The description and examples are to be regarded as illustrative in nature and not as restrictive.

[0141] It is to be understood that the application is not limited to the precise construction already described above and shown in the drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application should only be limited by the claims appended hereto.

Claims

1. A method for detecting concentrations of multiple gases canceling cross interference, characterized by, The method comprises the following steps: determining a target absorption spectrum interval corresponding to a to-be-detected gas, determining a target absorption spectrum according to the target absorption spectrum interval, and determining a target detection wavelength of each to-be-detected gas, wherein the target detection wavelength is a wavelength corresponding to a highest absorption peak of the to-be-detected gas in the target absorption spectrum, and the target absorption spectrum comprises an absorption spectrum of each to-be-detected gas in the target absorption spectrum interval; determining an interference gas of each to-be-detected gas according to the target detection wavelength of each to-be-detected gas, and performing spectral detection on each interference gas respectively to obtain an absorption spectrum of each interference gas; determining a relative absorbance coefficient of each interference gas at the target detection wavelength of other to-be-detected gases relative to the target detection wavelength of the interference gas itself according to the absorption spectrum of each interference gas; performing spectral detection on a mixed gas of all to-be-detected gases to obtain an absorption spectrum of the mixed gas; obtaining an absorbance of the to-be-detected gas with an independent peak according to the absorption spectrum of the mixed gas; calculating an actual absorbance of each to-be-detected gas at the target detection wavelength in the mixed gas according to the relative absorbance coefficient of each interference gas and the absorbance of the to-be-detected gas with the independent peak, comprising: establishing an absorbance equation group at the target detection wavelength of each to-be-detected gas in the mixed gas; bringing the relative absorbance coefficient of each interference gas and the absorbance of the to-be-detected gas with the independent peak into the absorbance equation group to obtain the actual absorbance of each to-be-detected gas in the mixed gas; the absorbance equation group is: ； wherein, is the relative absorbance coefficient of the target gas corresponding to the target detection wavelength; is the actual absorbance of the target gas at the respective target detection wavelength; is the superimposed sum of the absorbance corresponding to the target detection wavelength in the absorption spectrum of the mixed gas; is the quantity of the target gas; calculating the concentration of each to-be-detected gas in the mixed gas according to the actual absorbance of each to-be-detected gas at the target detection wavelength, comprising: obtaining a calibration function by using a standard gas detection method according to the relationship between gas absorbance and gas concentration; bringing the actual absorbance in the mixed gas into the calibration function to obtain the concentration of each to-be-detected gas in the mixed gas.

2. The method of claim 1, wherein the method is performed by the method of claim 1. The method of determining an interference gas of each to-be-detected gas according to the target detection wavelength of each to-be-detected gas comprises: determining other to-be-detected gases with a non-zero absorbance at the target detection wavelength of the to-be-detected gas, and determining the to-be-detected gases with the non-zero absorbance as the interference gas of the to-be-detected gas.

3. The method of claim 2, wherein the method is performed by the method of claim 1. The method of determining a relative absorbance coefficient of each interference gas at the target detection wavelength of other to-be-detected gases relative to the target detection wavelength of the interference gas itself according to the absorption spectrum of each interference gas comprises: determining a first absorbance of each interference gas at the target detection wavelength of itself; determining a second absorbance of each interference gas at the target detection wavelength of other to-be-detected gases; for each interference gas, taking a ratio of the second absorbance to the first absorbance as the relative absorbance coefficient of the interference gas.

4. The method of claim 1, wherein the method is a method of detecting concentrations of multiple gases by canceling cross interference, characterized by, The method comprises the following steps: In the target absorption spectrum, the independent peak is determined; In the absorption spectrum of the mixed gas, the absorbance of the to-be-detected gas with the independent peak is determined according to the independent peak; Wherein, the absorbance of the remaining to-be-detected gas corresponding to the independent peak is zero at the target detection wavelength.

5. The method of claim 1, wherein the method is used for detecting concentrations of multiple gases. The method comprises the following steps: The maximum wavelength and the minimum wavelength in the plurality of to-be-detected gases are determined; The target absorption spectrum interval is generated in the wavelength range covering the maximum wavelength and the minimum wavelength.

6. A system for detecting concentrations of multiple gases with elimination of cross-interference, characterized by The detection method for eliminating cross interference of multiple gas concentrations comprises the following steps: A signal generator is configured to output a modulation signal; A laser is connected to the signal generator and is configured to receive the modulation signal and output a first optical signal according to the modulation signal, wherein the output wavelength range of the first optical signal can cover a target absorption spectrum interval; A photoelectric detection module is configured to receive a second optical signal and convert the second optical signal into an electrical signal, wherein the second optical signal is a light signal with to-be-detected gas concentration information generated after the first optical signal is absorbed by the gas; A data acquisition module is connected to the photoelectric detection module and is configured to receive the electrical signal and convert the electrical signal into a digital signal; A host computer is connected to the data acquisition module and is configured to receive the digital signal, calculate the relative absorbance coefficient of each interfering gas at the target detection wavelength of other to-be-detected gases relative to the target detection wavelength of the interfering gas itself based on the digital signal, and calculate the actual absorbance of each to-be-detected gas at the target detection wavelength in the mixed gas according to the relative absorbance coefficient of each interfering gas and the absorbance of the to-be-detected gas with the independent peak. The host computer is further configured to calculate the concentration of each to-be-detected gas in the mixed gas according to the actual absorbance of each to-be-detected gas at the target detection wavelength.

7. The system for detecting concentrations of multiple gases according to claim 6, wherein Further comprising: A laser controller and a collimating lens; The laser controller is connected to the signal generator and the laser respectively and is configured to receive the modulation signal and control the wavelength of the light emitted by the laser according to the modulation signal to generate the first optical signal; The collimating lens is arranged on the light path of the optical signal and is configured to collimate the first optical signal.

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