Complex component VOCs detection device and detection method based on multi-channel mixed infrared absorption spectrum

Abstract

The application discloses a kind of complex component VOCs detection device and detection method based on multi-channel mixed infrared absorption spectrum, including the oil gas supply module for supplying pure air and gasoline, for the oil gas mixing module that pure air and gasoline are sufficiently mixed and the detection monitoring module for detecting the non-methane total concentration of oil gas in oil gas mixing module;Detection monitoring module includes respectively with the oil gas mixing module connection gas chromatograph and VOCs monitoring unit;VOCs monitoring unit includes VOCs sensor and data processor, the input end of data processor is respectively with the output of gas chromatograph and the output signal connection of VOCs sensor;Data processor is used to obtain the concentration signal C1 monitored by gas chromatograph and the concentration signal C2 detected by VOCs sensor, and according to concentration signal C1 and concentration signal C2 draw calibration work curve, then make concentration signal C2 with calibration work curve fitting, obtain non-methane total hydrocarbon concentration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field, and particularly relates to a complex component VOCs detection device and detection method based on multi-channel mixed infrared absorption spectrum. BACKGROUND

[0002] VOCs is volatile organic compounds, which refers to organic compounds with high saturated vapor pressure, low boiling point, small molecular weight and easy to volatilize at room temperature under standard conditions. This kind of substance is one of the main pollutants of atmosphere. Volatile organic compounds are usually divided into non-methane total hydrocarbons (abbreviated as NMHCs), oxygen-containing organic compounds, halogenated hydrocarbons, nitrogen-containing organic compounds, sulfur-containing organic compounds and several other categories. Non-methane total hydrocarbons in the atmosphere exceed a certain concentration, which is harmful to human health directly, and can also produce photochemical smog under certain conditions, causing harm to the environment and human beings.

[0003] At present, there are many methods for detecting non-methane total hydrocarbons in environmental air and industrial waste gas, but most countries use gas chromatography. The contents of total hydrocarbons and methane are measured by double-column double-hydrogen flame ionization detector (FID) gas chromatography, and the difference between the two is the content of non-methane total hydrocarbons. Double-column double-hydrogen flame ionization detector has high sensitivity and fast response, but the hydrogen flame ionization detector is easily affected by the surrounding gas in operation, which may affect the accuracy of detection. In addition, since the hydrogen flame ionization detector needs to burn gas frequently, it is easy to be damaged and worn out during use, and the parts need to be replaced regularly.

[0004] VOCs sensor is a kind of sensor for detecting volatile organic compounds. It is a very important environmental monitoring equipment, and VOCs sensor can be widely used in air quality monitoring, industrial process control, environmental monitoring and other fields. VOCs sensor generally adopts the most advanced photoionization PID sensing technology, has high sensitivity, low detection limit, high stability and other advantages, and can realize real-time monitoring and data analysis of PPB level VOCs gas. However, the current VOCs sensor is also easily affected by environmental humidity, temperature and interference gas, and when the VOCs composition is complex, it is easy to cause inaccurate detection results.

[0005] Therefore, in view of the current problem of inaccurate VOCs detection results, to develop a complex component VOCs detection device and detection method capable of improving the detection results of VOCs detection device is a technical problem to be solved at present. SUMMARY

[0006] The purpose of the present application is to provide a complex component VOCs detection device and detection method based on multi-channel mixed infrared absorption spectrum, so as to solve the problem that the current VOCs sensor is easy to cause inaccurate detection results when the VOCs composition is complex.

[0007] To address the aforementioned technical problems, in a first aspect, the present invention provides a complex component VOCs detection device based on multi-channel mixed-frequency infrared absorption spectroscopy, comprising an oil-gas supply module for supplying pure air and gasoline, an oil-gas mixing module for thoroughly mixing pure air and gasoline, and a detection and monitoring module for detecting the non-methane total concentration of the oil-gas mixture in the oil-gas mixing module; the detection and monitoring module includes a gas chromatograph and a VOCs monitoring unit respectively connected to the oil-gas mixing module; the VOCs monitoring unit includes a VOCs sensor and a data processor, the input terminal of the data processor being signal-connected to the output terminal of the gas chromatograph and the output terminal of the VOCs sensor respectively; the data processor is used to acquire the concentration signal C1 monitored by the gas chromatograph and the concentration signal C2 detected by the VOCs sensor, and to plot a calibration curve based on the concentration signals C1 and C2, and then to fit the concentration signal C2 with the calibration curve to obtain the non-methane total hydrocarbon concentration.

[0008] Furthermore, the VOCs sensor includes a gas cell with a gas cell inlet and a gas cell outlet. Inside the gas cell, a light source emitter and a detector are installed in cooperation with each other. The light source emitter is located at one end of the gas cell, and the detector is installed at the other end of the gas cell. The detector is connected to the input signal of the data processor through a data acquisition unit and a lock-in amplifier connected in sequence.

[0009] Furthermore, the VOCs monitoring unit also includes a power pump and a power supply circuit; the power pump is connected between the oil-gas mixing module and the gas pool inlet of the VOCs sensor, and the power supply circuit is used to power the VOCs sensor, data processor and power pump.

[0010] Furthermore, the power supply circuit includes a first voltage regulator circuit and a second voltage regulator circuit. The first voltage regulator circuit is connected between the power supply input terminal and the VOCs sensor and the data processor, and the second voltage regulator circuit is connected between the first voltage regulator circuit and the power pump.

[0011] Furthermore, a heater for heating the gas pool is provided at the bottom of the gas pool.

[0012] Furthermore, the oil-gas mixing module includes an oil-gas mixing box and an oil-gas mixer installed inside the oil-gas mixing box.

[0013] Secondly, the present invention provides a method for detecting the concentration of non-methane total hydrocarbons using the aforementioned complex component VOCs detection device, comprising the following steps:

[0014] S1: Acquire the concentration signal C1 output by the gas chromatograph;

[0015] S2: Acquire the concentration signal C2 output by the VOCs sensor;

[0016] S3: Plot the calibration curve with concentration signal C1 as the vertical axis and concentration signal C2 as the horizontal axis;

[0017] S4: Fit the concentration signal C2 to the calibration curve to obtain the concentration of non-methane total hydrocarbons.

[0018] Further, step S2 includes:

[0019] S21: Acquire the characteristic spectral signals (u1, u2, ..., u3) of multiple VOCs detected by the detector at different wavelengths. n );

[0020] S21: Combine multiple VOCs characteristic spectral signals (u1, u2, ..., u...) n They are converted into voltage signals respectively;

[0021] S22: Extract the frequency feature information of the voltage signals corresponding to multiple VOCs characteristic spectral signals respectively, to obtain multiple frequency feature signals (f1, f2, ..., f...). n );

[0022] S23: Extract feature signals at multiple frequency points (f1, f2, ..., f...) respectively. n The amplitude information of the wave is used to obtain multiple phase-locked signals (S1, S2, ..., S...). n ).

[0023] Furthermore, in step S22, the FFT algorithm is used to extract the frequency feature information of the voltage signals corresponding to the feature spectral signals of multiple VOCs respectively.

[0024] Furthermore, in step S23, a multi-channel lock-in amplifier is used to extract the amplitude information of multiple frequency point characteristic signals.

[0025] Furthermore, step S4 specifically includes:

[0026] S41: Obtain the working curve matrix Ms based on the calibration working curve;

[0027] S42: Enables multiple phase-locked signals (S1, S2, ..., S...) n Multiply by the working curve matrix Ms to obtain the total non-methane hydrocarbon concentration.

[0028] The beneficial effects of this invention are as follows: by using a gas chromatograph and a VOCs sensor to detect VOCs respectively, and then plotting a calibration curve based on the concentration signal C1 detected by the gas chromatograph and the concentration signal C2 detected by the VOCs sensor, and fitting the concentration signal C2 with the calibration curve, a high-precision VOCs working curve calibration can be achieved, and a high-confidence VOCs concentration detection result can be obtained. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, use the same reference numerals to denote the same or similar parts. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 This is a schematic diagram of one embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of a VOCs monitoring unit according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a VOCs sensor according to an embodiment of the present invention;

[0033] The components include: 1. Air tank; 2. Gasoline bottle; 3. Gas-oil mixing chamber; 5. Gas chromatograph; 6. VOCs monitoring unit; 61. Power pump; 62. VOCs sensor; 621. Light source emitter; 622. Gas pool inlet; 623. Gas pool; 624. Heating element; 625. Gas pool outlet; 626. Detector; 627. Data acquisition unit; 63. First voltage regulator circuit; 64. Microcontroller; 65. Second voltage regulator circuit; 66. Air inlet; 661. Filter; 67. Air outlet; 68. Data transmission interface; 69. Power input interface. Detailed Implementation

[0034] like Figure 1 The illustrated VOCs detection device based on multi-channel mixed-frequency infrared absorption spectroscopy includes an oil-gas supply module for supplying clean air and gasoline, an oil-gas mixing module for thoroughly mixing clean air and gasoline, and a detection and monitoring module for detecting the total non-methane concentration of the oil-gas mixture in the oil-gas mixing module. The oil-gas supply module includes an air tank 1 for supplying clean air and a gasoline bottle 2 for supplying gasoline. The detection and monitoring module includes a gas chromatograph 5 and a VOCs monitoring unit 6, which are respectively connected to the oil-gas mixing module. The VOCs monitoring unit 6 includes a VOCs sensor 62 and a data processor. The input terminal of the data processor is connected to the output terminal of the gas chromatograph 5 and the output terminal of the VOCs sensor 62. The data processor is used to acquire the concentration signal C1 detected by the gas chromatograph 5 and the concentration signal C2 detected by the VOCs sensor 62, and to plot a calibration curve based on the concentration signals C1 and C2. Then, the concentration signal C2 is fitted to the calibration curve to obtain the total non-methane hydrocarbon concentration.

[0035] This device uses a gas chromatograph 5 and a VOCs sensor 62 to detect VOCs. Then, a calibration curve is plotted based on the concentration signal C1 detected by the gas chromatograph 5 and the concentration signal C2 detected by the VOCs sensor 62. The concentration signal C2 is then fitted to the calibration curve to achieve high-precision VOCs calibration and obtain high-confidence VOCs concentration detection results. A microcontroller 64 can be used as the data processor. The microcontroller 64 outputs the calculated VOCs concentration detection results, thus providing the accurate non-methane total hydrocarbon concentration.

[0036] The VOCs sensor 62 supports data upload via HJ45 and RS485. RS485: baud rate 9600, 1 stop bit, 8 data bits, None parity, hexadecimal. RJ45: protocol type TCP server, local host address 192.168.1.7, local host port 8000, hexadecimal. Uploaded data includes frame header, data length, sensor serial number, non-methane total hydrocarbon content, and fault code. Data will be uploaded to the data acquisition platform according to the following communication protocol format.

[0037] According to one embodiment of this application, the VOCs sensor 62 includes a gas cell 623, which has a gas cell inlet 622 and a gas cell outlet 625. A light source emitter 621 and a detector 626 are installed inside the gas cell 623, cooperating with each other. The light source emitter 621 is located at one end of the gas cell 623, and the detector 626 is installed at the other end. The detector 626 is connected to the input terminal of a data processor via a data acquisition unit 627 and a lock-in amplifier connected in sequence. The light source in the gas cell 623 emits near-infrared light to the detector 626. When non-methane hydrocarbons enter the gas cell 623, the absorption spectrum of the near-infrared light changes, and the signal value received by the detector 626 also changes with the concentration of non-methane hydrocarbons.

[0038] The VOCs sensor 62 adopts a physical structure of a single light source and a single detector 626, and then uses a multi-channel mixed-frequency infrared absorption spectroscopy detection algorithm to achieve high-precision regression calibration of complex VOCs gas components. The resulting VOCs sensor 62 has innovative features such as small size, stable structure, accurate measurement and extremely high precision.

[0039] According to one embodiment of this application, the VOCs monitoring unit 6 further includes a power pump 61 and a power supply circuit; the power pump 61 is connected between the oil-gas mixing module and the gas pool 623 inlet 622 of the VOCs sensor 62, and the power supply circuit is used to supply power to the VOCs sensor 62, the data processor, and the power pump 61. Non-methane total hydrocarbons are drawn into the VOCs sensor 62 under the action of the power pump 61; the VOCs system adopts a wide voltage input of 9-24V.

[0040] According to one embodiment of this application, the power supply circuit includes a first voltage regulator circuit 63 and a second voltage regulator circuit 65. The first voltage regulator circuit 63 is connected between the power supply input terminal and the VOCs sensor 62 and the data processor, and the second voltage regulator circuit 65 is connected between the first voltage regulator circuit 63 and the power pump 61. The first voltage regulator circuit 63 converts the input voltage into a 12V voltage to directly power the microcontroller 64 and the VOCs sensor 62, and the second voltage regulator circuit 65 converts the 12V voltage of the first voltage regulator circuit 63 into a 5V voltage to power the heater of the VOCs sensor 62.

[0041] According to one embodiment of this application, a heater for heating the gas chamber 623 is provided at the bottom of the gas chamber 623. The heater can provide temperature compensation for the VOCs sensor 62, preventing the readings of the VOCs sensor 62 from drifting.

[0042] According to one embodiment of this application, the air inlet 66 of the VOCs monitoring unit 6 is further provided with a filter 661 for filtering the gas entering the VOCs sensor 62 to avoid the humidity of VOCs affecting the monitoring results.

[0043] According to one embodiment of this application, the oil-gas mixing module includes an oil-gas mixing box 3 and an oil-gas mixer installed in the oil-gas mixing box 3.

[0044] Secondly, the present invention provides a method for detecting the concentration of non-methane total hydrocarbons using the aforementioned complex component VOCs detection device, comprising the following steps:

[0045] S1: Acquire the concentration signal C1 output by gas chromatograph 5;

[0046] S2: Acquire the concentration signal C2 output by VOCs sensor 62;

[0047] S3: Plot the calibration curve with concentration signal C1 as the vertical axis and concentration signal C2 as the horizontal axis;

[0048] S4: Fit the concentration signal C2 to the calibration curve to obtain the concentration of non-methane total hydrocarbons.

[0049] According to one embodiment of this application, step S2 includes:

[0050] S21: Acquire the characteristic spectral signals (u1, u2, ..., u3) of multiple VOCs detected by detector 626 at different wavelengths. n );

[0051] S21: Combine multiple VOCs characteristic spectral signals (u1, u2, ..., u...) n They are converted into voltage signals respectively;

[0052] S22: Extract the frequency feature information of the voltage signals corresponding to multiple VOCs characteristic spectral signals respectively, and obtain multiple frequency feature signals (f1, f2, ..., f...). n );

[0053] S23: Extract feature signals at multiple frequency points (f1, f2, ..., f) respectively. n The amplitude information of the wave is used to obtain multiple phase-locked signals (S1, S2, ..., S...). n ).

[0054] According to one embodiment of this application, in step S22, the FFT algorithm is used to extract the frequency feature information of the voltage signals corresponding to the multiple VOCs feature spectral signals.

[0055] According to one embodiment of this application, in step S23, a multi-channel lock-in amplifier is used to extract the amplitude information of multiple frequency point characteristic signals respectively.

[0056] According to one embodiment of this application, step S4 specifically includes:

[0057] S41: Obtain the working curve matrix Ms based on the calibration working curve;

[0058] S42: Enables multiple phase-locked signals (S1, S2, ..., S...) n Multiply by the working curve matrix Ms to obtain the total non-methane hydrocarbon concentration.

[0059] Since VOCs have a wide absorption spectrum in the infrared band, multiple mechanical modulators of different frequencies can be used to measure the characteristic absorption spectra of multiple VOCs in order to achieve high-precision VOCs detection. The infrared modulation frequency corresponding to each band is different. Through the detector 626, the detection of infrared photoelectric signals superimposed in multiple frequency domains is realized. The detection results are used to extract frequency points using the FFT algorithm, and the multinomial correlation matrix method is used to calibrate multiple frequency domain signals individually. Then, oil and gas are introduced to perform correlation matrix fitting measurement, and finally, the calibration of high-precision VOC working curve is achieved.

[0060] The following example demonstrates the measurement of the characteristic absorption spectra of three VOCs at 3µm, 7µm, and 13µm. An optical signal to voltage signal conversion is performed on a photodetector 626, and the FFT algorithm is used for frequency extraction to obtain a superimposed optical signal with three frequency components: 3µm + 7µm + 13µm. The corresponding frequency features are f3, f7, and f... 13 Then, using a three-channel lock-in amplifier, f3, f7, and f8 are extracted from the voltage signal of the photodetector 626. 13The amplitude of each frequency point is different because the infrared modulation frequency corresponding to each band is different, thus resulting in three sets of phase-locked signals S3, S7, and S8 at three independent frequency points. 13 .

[0061] The three lock-in signals mentioned above are connected in series with gas chromatograph 5, and the detection result of gas chromatograph 5 is used as the actual VOCs concentration, and is used as the ordinate; S3, S7 and S 13 The three working curves are calibrated using the horizontal axis as the abscissa, and a calibration matrix Ms is formed that takes into account the temperature, pressure and power of the laser emitter in the gas cell.

[0062] In actual measurements, by obtaining (S3, S7, S...) 13 The phase-locked signal matrix is ​​multiplied by the calibration working curve matrix Ms to obtain the high-confidence VOCs concentration detection result (1). Finally, the VOCs concentration detection result is output through the 10P pin to obtain the accurate non-methane total hydrocarbon concentration.

[0063] This algorithm addresses the challenges of complex VOCs composition and low single-wavelength calibration accuracy, achieving a signal calibration regression accuracy better than 1%.

[0064]

[0065] Wherein, S3, S7, and S13 are phase-locked signals of 3um, 7um, and 13um, respectively; C is the actual VOCs concentration; Ms is the calibration matrix; Kmn is the calibration matrix; a is the temperature inside the gas cell (K); b is the gas pressure inside the gas cell (MPa); and c is the laser emitter power (W).

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for detecting complex VOCs based on multi-channel mixed-frequency infrared absorption spectroscopy, characterized in that, The system includes an oil-gas supply module for supplying clean air and gasoline, an oil-gas mixing module for thoroughly mixing the clean air and gasoline, and a detection and monitoring module for detecting the total non-methane concentration of the oil-gas mixture in the oil-gas mixing module. The detection and monitoring module includes a gas chromatograph and a VOCs monitoring unit, both connected to the oil-gas mixing module. The VOCs monitoring unit includes a VOCs sensor and a data processor. The input terminal of the data processor is connected to the output terminal of the gas chromatograph and the output terminal of the VOCs sensor, respectively. The data processor is used to acquire the concentration information detected by the gas chromatograph. The concentration signals C1 and C2 detected by the VOCs sensor are used to generate a calibration curve. Then, the concentration signal C2 is fitted to the calibration curve to obtain the non-methane total hydrocarbon concentration. The VOCs sensor includes a gas cell with an inlet and an outlet. A light source emitter and a detector are installed inside the gas cell, with the emitter at one end and the detector at the other. The detector is connected to the input of the data processor via a data acquisition unit and a lock-in amplifier connected in sequence. The data processor obtains the non-methane total hydrocarbon concentration using the following method: S1: Acquire the concentration signal C1 output by the gas chromatograph; S2: Acquire the concentration signal C2 output by the VOCs sensor; step S2 includes: S21: Acquire the characteristic spectral signals (u1, u2, ..., u) of multiple VOCs detected by the detector at different wavelengths. n ); S21: The multiple VOCs characteristic spectral signals (u1, u2, ..., u...) are processed... n They are converted into voltage signals respectively; S22: Extract the frequency feature information of the voltage signals corresponding to the multiple VOCs characteristic spectral signals respectively, to obtain multiple frequency feature signals (f1, f2, ..., f...). n ); S23: Extract the multiple frequency point feature signals (f1, f2, ..., f) respectively. n The amplitude information of the phase lock signal (S1, S2, ..., S) is used to obtain multiple phase lock signals (S1, S2, ..., S). n ); S3: Plot the calibration curve using the concentration signal C1 as the vertical axis and the concentration signal C2 as the horizontal axis; S4: Fit the concentration signal C2 to the calibration curve to obtain the non-methane total hydrocarbon concentration; step S4 specifically includes: S41: Obtain the working curve matrix Ms based on the calibration working curve; S42: Enable the multiple phase-locked signals (S1, S2, ..., S...) n Multiply by the working curve matrix Ms to obtain the total non-methane hydrocarbon concentration.

2. The complex component VOCs detection device based on multi-channel mixed-frequency infrared absorption spectroscopy according to claim 1, characterized in that, The VOCs monitoring unit also includes a power pump and a power supply circuit; the power pump is connected between the oil-gas mixing module and the gas pool inlet of the VOCs sensor, and the power supply circuit is used to supply power to the VOCs sensor, the data processor and the power pump.

3. The complex component VOCs detection device based on multi-channel mixed-frequency infrared absorption spectroscopy according to claim 2, characterized in that, The power supply circuit includes a first voltage regulator circuit and a second voltage regulator circuit. The first voltage regulator circuit is connected between the power supply input terminal and the VOCs sensor and the data processor, and the second voltage regulator circuit is connected between the first voltage regulator circuit and the power pump.

4. The complex component VOCs detection device based on multi-channel mixed-frequency infrared absorption spectroscopy according to claim 1, characterized in that, The bottom of the gas pool is equipped with a heater for heating the gas pool.

5. A method for detecting the concentration of non-methane total hydrocarbons using the complex component VOCs detection device according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Acquire the concentration signal C1 output by the gas chromatograph; S2: Acquire the concentration signal C2 output by the VOCs sensor; step S2 includes: S21: Acquire the characteristic spectral signals (u1, u2, ..., u) of multiple VOCs detected by the detector at different wavelengths. n ); S21: The multiple VOCs characteristic spectral signals (u1, u2, ..., u...) are processed... n They are converted into voltage signals respectively; S22: Extract the frequency feature information of the voltage signals corresponding to the multiple VOCs characteristic spectral signals respectively, to obtain multiple frequency feature signals (f1, f2, ..., f...). n ); S23: Extract the multiple frequency point feature signals (f1, f2, ..., f) respectively. n The amplitude information of the phase lock signal (S1, S2, ..., S) is used to obtain multiple phase lock signals (S1, S2, ..., S). n ); S3: Plot the calibration curve using the concentration signal C1 as the vertical axis and the concentration signal C2 as the horizontal axis; S4: Fit the concentration signal C2 to the calibration curve to obtain the non-methane total hydrocarbon concentration; step S4 specifically includes: S41: Obtain the working curve matrix Ms based on the calibration working curve; S42: Enable the multiple phase-locked signals (S1, S2, ..., S...) n Multiply by the working curve matrix Ms to obtain the total non-methane hydrocarbon concentration.

6. The method for detecting the concentration of non-methane total hydrocarbons according to claim 5, characterized in that, In step S22, the FFT algorithm is used to extract the frequency feature information of the voltage signals corresponding to the multiple VOCs feature spectral signals.

7. The method for detecting the concentration of non-methane total hydrocarbons according to claim 5 or 6, characterized in that, In step S23, a multi-channel lock-in amplifier is used to extract the amplitude information of multiple frequency point characteristic signals respectively.

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