Separation and identification device and method for cross interference of methane and ethane in oil type gas

Abstract

The invention relates to the technical field of mine gas monitoring, in particular to an oil type gas methane and ethane cross interference separation and identification device and method, and the device comprises a control module, a laser I, a laser II, a light path transmission device I, a light path transmission device II, an optical miniature cavity, a dichroscope, a photoelectric detector and a tuning fork sensor; two paths of different voltage waveform signals are generated; the two lasers are driven to respectively generate emergent laser of methane and ethane gas spectral absorption wavelengths; the two paths of laser beams are split through a dichroscope, same-frequency resonance optical signals reflected by the dichroscope are collected, and optical signals transmitted by the dichroscope are collected; demodulating to obtain mixed spectrum data of methane and ethane gas, inputting the mixed spectrum data into a spectrum analysis model, and outputting methane and ethane independent spectrums separated from the mixed spectrum data. The spectrum mean absolute error is used as a similarity evaluation index, and independent spectrums of methane and ethane can be effectively separated and accurately judged.

Description

Technical Field

[0001] This invention relates to the field of mine gas monitoring technology, specifically to a device and method for separating and identifying cross-interference between methane and ethane in oil-type gas. Background Technology

[0002] Oil-type gas is a new, hidden geological factor posing a hazard in coal-oil-gas coexisting mines, and it is an unavoidable and urgent problem to be solved for the safe and efficient mining of such mines. The gas-oil-type gas mixture is a composite gas composed of coal seam gas and surrounding rock oil-type gas, characterized by low coal seam gas content, large outburst volume, highly random outburst time and location, and high difficulty in prevention and control. During coal mining operations, oil-type gas can easily trigger gas exceedance accidents, seriously threatening mine production safety and personnel safety.

[0003] Therefore, high-sensitivity monitoring of methane and ethane, the main components of oil-type gases, is particularly important and urgent. Traditional gas measurement methods, such as chemical analysis, while capable of detecting these two gases to some extent, suffer from low sensitivity and require lengthy calibration processes, making them unsuitable for the rapid and accurate monitoring needs of mine sites. In contrast, TDLAS (Tunable Diode Laser Absorption Spectroscopy) technology demonstrates high accuracy and reliability in methane measurement, effectively meeting the requirements for methane monitoring. However, for ethane measurement, due to the different absorption characteristics of ethane molecules, relying solely on existing TDLAS technology has limitations. Increasing the length of the absorption cell is necessary to improve measurement sensitivity and ensure accurate ethane detection. Therefore, further optimization and improvement of TDLAS technology to achieve ideal results in ethane measurement is a pressing technical challenge that needs to be overcome. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a device for separating and identifying cross-interference between oil-type methane and ethane, comprising a control module, a laser I, a laser II, an optical path transmission device I, an optical path transmission device II, an optical microcavity, a dichroic mirror, a photodetector, and a tuning fork sensor. The control module is used to generate two different laser modulation voltage signals, which are respectively applied to two laser drivers to generate laser driving currents, which act on laser one and laser two to make them emit light; it is also used to receive the acquisition signals from the photodetector and the tuning fork sensor respectively, and demodulate the two acquisition signals respectively, and separate the overlapping spectra of methane and ethane gases through a spectral analysis model. Laser 1 and Laser 2 are used to receive laser driving current and generate output laser; Optical path transmission device one and optical path transmission device two are used to transmit the laser beams of laser one and laser two to the optical microcavity, respectively. An optical microcavity is used to fill the gas to be tested, provide an optical path for two incident laser beams, and guide the output of the laser beams; Dichroic mirrors are used to split laser beams emitted from optical microcavities; A photodetector is used to receive light signals carrying gas absorption information transmitted through a dichroic mirror and convert the light signals into electrical signals. The tuning fork sensor is used to collect the absorption signal of the same frequency resonant light after reflection from the dichroic mirror, and convert the collected same frequency resonant light absorption signal into an electrical signal, which is then transmitted to the control module for signal demodulation processing.

[0005] The control module is electrically connected to laser one and laser two respectively. The light emitted from laser one is horizontally incident on the optical microcavity through optical path transmission device one; the light emitted from laser two is incident on the optical microcavity at a fixed incident angle through optical path transmission device two; a dichroic mirror is set at the rear end of the optical microcavity, the photodetector is set on the transmission light path of the dichroic mirror, and the tuning fork sensor is set on the reflection light path of the dichroic mirror. The signal output terminals of the photodetector and the tuning fork sensor are electrically connected to the control module.

[0006] The optical path transmission device includes an optical collimator and an optical lens, with the optical lens located at the rear end of the optical collimator.

[0007] The second optical path transmission device includes an optical collimator, an acousto-optic modulator, and several optical matching lenses. The acousto-optic modulator is located at the rear end of the optical collimator, and several optical matching lenses are arranged at the rear end of the acousto-optic modulator.

[0008] In a specific embodiment, the optical microcavity is composed of high-reflectivity lenses.

[0009] Both laser one and laser two are DFB lasers.

[0010] On the other hand, a method for separating and identifying cross-interference between oil-type methane and ethane in oil-type gases, applied to the separation and identification device for cross-interference between oil-type methane and ethane as described above, is provided, comprising: By generating two different voltage waveform signals, one being a superposition of a sawtooth wave and a sine wave, and the other being a single sawtooth wave signal; the two voltage waveform signals are converted into laser modulation voltage signals, which synchronously drive two lasers to generate emitted lasers with the absorption wavelengths of methane and ethane gas spectra, respectively. Laser 1 is horizontally incident into the optical microcavity via optical path transmission device 1, and laser 2 is modulated by an acousto-optic modulator and coupled into the same optical microcavity through optical matching lens; Two laser beams are split by a dichroic mirror, and the same-frequency resonant light signal reflected by the dichroic mirror is collected by a tuning fork sensor, while the light signal transmitted by the dichroic mirror is collected by a photodetector. The acquisition signals from the tuning fork sensor and photodetector are simultaneously acquired and demodulated to obtain mixed spectral data of methane and ethane gases. This data is then input into an artificial intelligence-based spectral analysis model, which outputs the independent spectra of methane and ethane after separation of the mixed spectral data.

[0011] The sawtooth wave and sine wave superposition signal is used to drive laser one to generate an emitted laser with a wavelength of 1.65 μm that absorbs the spectrum of methane gas; the single sawtooth wave signal is used to drive laser two to generate an emitted laser with a wavelength of 1.68 μm that absorbs the spectrum of ethane gas.

[0012] The spectral analysis model was trained through the following operations: Construct a dataset; obtain the absorption spectra of methane, ethane, and mixed gases under preset experimental conditions, and establish a spectral data simulation dataset by introducing system noise, which includes optical microcavity noise and detector noise; The constructed spectral data simulation dataset is divided into several subsets to train the spectral analysis model, and each subset is used as a validation set to adjust the hyperparameters in turn. The Adam optimizer is used to accelerate convergence. After all hyperparameters are determined, optimization is performed using the complete dataset. The mean absolute error of the two spectra is used as the similarity evaluation index.

[0013] The spectral analysis model determines the accuracy of separation using a similarity evaluation index. If the similarity evaluation index is less than a preset threshold, then the independent spectra of methane and ethane are determined to be effectively separated. The formula for the similarity evaluation index is: , In the formula, n is the number of spectral sampling points; and Representing the predicted spectrum and the true spectral value respectively. The value of each sampling point.

[0014] Beneficial Effects: This invention provides a device and method for separating and identifying cross-interference between oil-based methane and ethane gases. The device precisely generates two different laser modulation voltage signals to drive lasers, causing lasers one and two to emit outgoing laser light at the absorption wavelengths of methane and ethane gases, respectively. The optical microcavity utilizes high-reflectivity lenses to provide different optical path lengths for lasers at different incident angles, meeting the different absorption cell length requirements of methane and ethane gases. Different optical path lengths are achieved through different incident angles and reflection times, simplifying the device structure, reducing costs, and ensuring measurement effectiveness. Simultaneously, by generating two specific laser beams, the spectral absorption of methane and ethane at specific wavelengths is excited. Using an AI-based spectral analysis model for mixed spectral data processing, and employing the mean absolute error of the spectra as a similarity evaluation index, the system can effectively separate and accurately determine the independent spectra of methane and ethane, achieving high-precision gas separation and identification. Attached Figure Description

[0015] The solutions and advantages of this application will become clear to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0016] In the attached diagram: Figure 1 This is a schematic diagram of a device for separating and identifying cross-interference between oil-based methane and ethane. Detailed Implementation

[0017] Exemplary embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings.

[0018] See Figure 1 This embodiment provides a device for separating and identifying cross-interference between oil-type methane and ethane gases, including a control module, a first laser, a second laser, an optical path transmission device, an optical path transmission device, an optical microcavity, a dichroic mirror, a photodetector, and a tuning fork sensor. The control module is electrically connected to both lasers. Light emitted from laser one is horizontally incident on the optical microcavity via optical path transmission device one; light emitted from laser two is incident on the optical microcavity at a fixed angle via optical path transmission device one. A dichroic mirror is positioned at the rear end of the optical microcavity. The photodetector is positioned on the transmitted light path of the dichroic mirror, and the tuning fork sensor is positioned on the reflected light path of the dichroic mirror. The signal output terminals of the photodetector and the tuning fork sensor are electrically connected to the control module.

[0019] To achieve drive control of the control module, the control module includes an ARM control board, a digital-to-analog converter (DAC), a data acquisition card, and two laser drivers. The ARM control board is electrically connected to the DAC and the data acquisition card. The DAC is connected to the two laser drivers, each with an external laser source (laser one and laser two). The data acquisition card is connected to the serial communication ports of the signal output terminals of the photodetector and the tuning fork detector.

[0020] The control module is used to generate two different laser modulation voltage signals through the ARM control board, which are respectively applied to two laser drivers to generate laser driving currents, which act on laser one and laser two to make them emit light; it is also used to receive the acquisition signals from the photodetector and the tuning fork sensor through the data acquisition card, and demodulate the two acquisition signals respectively, and separate the overlapping spectra of methane and ethane gases through the spectral analysis model.

[0021] Laser 1 and Laser 2 are used to receive laser driving current to generate emitted laser light. Both laser 1 and Laser 2 are DFB lasers. DFB lasers achieve single longitudinal mode output through built-in Bragg gratings. The linewidth is generally less than 1MHz, the side-mode suppression ratio can reach more than 40-50dB, and the spectral purity is high. Its grating structure has low sensitivity to temperature and current changes, and the wavelength drift is less than 0.1nm / ℃, making it suitable for long-term temperature transmission.

[0022] The optical path transmission device one and optical path transmission device two are used to transmit the laser beams of laser one and laser two to the optical microcavity, respectively.

[0023] To enable laser one and laser two to be incident on the optical microcavity at different angles, the optical path transmission device one includes an optical collimator and an optical lens. The optical lens is located at the rear end of the optical collimator. The optical collimator is used to convert the emitted laser into a parallel laser beam, limit the direction and angle of the emitted laser, reduce scattering interference, and control the irradiation area. The optical lens can focus the parallel laser beam onto the entrance of the optical microcavity.

[0024] The second optical transmission device includes an optical collimator, an acousto-optic modulator, and several optical matching lenses. The acousto-optic modulator is located at the rear end of the optical collimator, and several optical matching lenses are arranged at the rear end of the acousto-optic modulator. The acousto-optic modulator is used to control the laser power, modulate the laser beam, and generate a stable laser pulse sequence with a preset linewidth. The optical matching lenses are used to reflect the laser beam emitted by the acousto-optic modulator and incident it onto the optical microcavity at a fixed angle.

[0025] The optical microcavity is used to fill the gas to be tested, provide optical paths for the two incident laser beams, and guide the laser beam output. Furthermore, to accommodate the different absorption cell lengths of methane and ethane gases using a single optical microcavity, the microcavity is composed of high-reflectivity lenses. When laser one is incident horizontally into the microcavity, it is not reflected, resulting in a shorter optical path. When laser two is incident obliquely into the microcavity, it undergoes multiple reflections, resulting in a longer optical path. This allows for two transmission optical paths for laser beams of different wavelengths.

[0026] Dichroic mirrors are used to split laser beams emitted from optical microcavities.

[0027] A photodetector is used to receive light signals carrying gas absorption information transmitted through a dichroic mirror and convert the light signals into electrical signals.

[0028] The tuning fork sensor is used to collect the same-frequency resonant light absorption signal after reflection from the dichroic mirror, and converts the collected same-frequency resonant light absorption signal into an electrical signal, which is then transmitted to the control module for signal demodulation processing.

[0029] Furthermore, based on the aforementioned separation and identification device for cross-interference between methane and ethane in oil-type gases, this embodiment also provides a method for separating and identifying the cross-interference between methane and ethane in oil-type gases. This method is used to separate the overlapping spectra of methane and ethane gases in oil-type gases, and its steps are as follows: S1. By generating two different voltage waveform signals, one is a superposition signal of sawtooth wave and sine wave, and the other is a single sawtooth wave signal; the two voltage waveform signals are converted into laser modulation voltage signals, which synchronously drive the two lasers to generate emitted lasers with the absorption wavelengths of methane and ethane gas spectra respectively. In this embodiment, the sawtooth wave and sine wave superposition signal is used to drive laser one to generate an emitted laser with a wavelength of 1.65 μm that absorbs the spectrum of methane gas; the single sawtooth wave signal is used to drive laser two to generate an emitted laser with a wavelength of 1.68 μm that absorbs the spectrum of ethane gas.

[0030] S2. Laser 1 is horizontally incident into the optical microcavity via optical path transmission device 1. Laser 2 is modulated by an acousto-optic modulator and coupled into the same optical microcavity through an optical matching lens. S3. The two laser beams are split by a dichroic mirror, and the same frequency resonant light signal reflected by the dichroic mirror is collected by a tuning fork sensor, and the light signal transmitted by the dichroic mirror is collected by a photodetector. In order for the tuning fork sensor to receive and collect the transmitted light signal, the sawtooth wave and sine wave superposition signal generated by the ARM control board are the same as the tuning fork resonance frequency of the tuning fork detector.

[0031] S4. Simultaneously acquire the acquisition signals from the tuning fork sensor and photodetector, demodulate them to obtain the mixed spectral data of methane and ethane gases, and input them into the artificial intelligence-based spectral analysis model to output the independent spectra of methane and ethane after separating the mixed spectral data. When laser beams illuminate the optical microcavity, each beam is absorbed by a gas whose wavelength matches the corresponding gas spectrum absorption wavelength, resulting in a photoacoustic effect. The signals acquired by the tuning fork sensor and photodetector are converted into current signals, which are proportional to the gas absorption intensity, as shown in the formula: Where I(t) represents the current signal; Ci Indicates gas concentration; λ (t) represents the laser wavelength; σ i Indicates the gas absorption cross section; P 0 This indicates the output laser power.

[0032] The second harmonic signal is extracted by performing phase-locked demodulation on the current signal. This phase-locked demodulation process is existing technology and will not be described in detail here. Since the current signal is proportional to the gas absorption intensity, the second harmonic signal after phase-locked demodulation is a voltage value, also proportional to the gas absorption intensity. A linear relationship is established between the gas absorption intensity and the second harmonic signal to obtain mixed spectral data.

[0033] To ensure the proper identification and separation of mixed gas spectral data by the spectral analysis model, the model is trained using a backpropagation (BP) neural network. The operation of this model is as follows: A dataset is constructed; the absorption spectra of methane, ethane, and mixed gases under preset experimental conditions are obtained through the High-Precision Transfer Molecular Absorption Database (HITRAN), and a spectral data simulation dataset is established by introducing system noise, including optical microcavity noise and detector noise; The constructed spectral data simulation dataset is divided into several subsets to train the spectral analysis model, and each subset is used as a validation set to adjust the hyperparameters in turn. The Adam optimizer is used to accelerate convergence, and after all hyperparameters are determined, optimization is performed using the complete dataset. The mean absolute error of the two spectra is used as the similarity evaluation index, and its formula is as follows: , In the formula, n is the number of spectral sampling points; and Representing the predicted spectrum and the true spectral value respectively. The values ​​of each sampling point. By observing the MAE of the spectrum, the subtle differences between the two can be more intuitively discovered, thus enabling a correct assessment of the model performance when they are difficult to distinguish with the naked eye.

[0034] The spectral analysis model separates mixed spectral data as follows: Input measured mixed spectral data, perform gas identification and separation, and output the separate independent spectra of methane and ethane; The accuracy of separation is determined by a similarity evaluation index. If the similarity evaluation index is less than a preset threshold, then the independent spectra of methane and ethane are determined to be effectively separated.

[0035] Based on the separated independent spectra of methane and ethane, the absorbance of a single spectrum can be obtained. The concentration of a single gas can be calculated by dividing the absorbance by the gas absorption cross section of the spectrum corresponding to each absorbing molecule and the transmission optical path of the optical microcavity.

Claims

1. A separation and identification device for cross-interference between oil-based methane and ethane, characterized in that, It includes a control module, laser one, laser two, optical path transmission device one, optical path transmission device two, optical microcavity, dichroic mirror, photodetector and tuning fork sensor; The control module is used to generate two different laser modulation voltage signals, which are respectively applied to two laser drivers to generate laser driving currents, which act on laser one and laser two to make them emit light; it is also used to receive the acquisition signals from the photodetector and the tuning fork sensor respectively, and demodulate the two acquisition signals respectively, and separate the overlapping spectra of methane and ethane gases through a spectral analysis model. Laser 1 and Laser 2 are used to receive laser driving current and generate output laser; Optical path transmission device one and optical path transmission device two are used to transmit the laser beams of laser one and laser two to the optical microcavity, respectively. An optical microcavity is used to fill the gas to be tested, provide an optical path for two incident laser beams, and guide the output of the laser beams; Dichroic mirrors are used to split laser beams emitted from optical microcavities; A photodetector is used to receive light signals carrying gas absorption information transmitted through a dichroic mirror and convert the light signals into electrical signals. The tuning fork sensor is used to collect the absorption signal of the same frequency resonant light after reflection from the dichroic mirror, and convert the collected same frequency resonant light absorption signal into an electrical signal, which is then transmitted to the control module for signal demodulation processing.

2. The separation and identification device for cross-interference between oil-type methane and ethane as described in claim 1, characterized in that, The control module is electrically connected to laser one and laser two respectively. The light emitted from laser one is horizontally incident on the optical microcavity through optical path transmission device one; the light emitted from laser two is incident on the optical microcavity at a fixed incident angle through optical path transmission device two; a dichroic mirror is set at the rear end of the optical microcavity, the photodetector is set on the transmission light path of the dichroic mirror, and the tuning fork sensor is set on the reflection light path of the dichroic mirror. The signal output terminals of the photodetector and the tuning fork sensor are electrically connected to the control module.

3. The separation and identification device for cross-interference between oil-type methane and ethane according to claim 2, characterized in that, The optical path transmission device includes an optical collimator and an optical lens, with the optical lens located at the rear end of the optical collimator.

4. The separation and identification device for cross-interference between oil-type methane and ethane according to claim 2, characterized in that, The second optical path transmission device includes an optical collimator, an acousto-optic modulator, and several optical matching lenses. The acousto-optic modulator is located at the rear end of the optical collimator, and several optical matching lenses are arranged at the rear end of the acousto-optic modulator.

5. The separation and identification device for cross-interference between oil-type methane and ethane according to claim 1, characterized in that, The optical microcavity is composed of high-reflectivity lenses.

6. The separation and identification device for cross-interference between oil-type methane and ethane as described in claim 1, characterized in that, Both laser one and laser two are DFB lasers.

7. A method for separating and identifying cross-interference between oil-type methane and ethane in an oil-type gas using the separation and identification device for cross-interference between oil-type methane and ethane as described in any one of claims 1-6, characterized in that, include: By generating two different voltage waveform signals, one being a superposition of a sawtooth wave and a sine wave, and the other being a single sawtooth wave signal; the two voltage waveform signals are converted into laser modulation voltage signals, which synchronously drive two lasers to generate emitted lasers with the absorption wavelengths of methane and ethane gas spectra, respectively. Laser 1 is horizontally incident into the optical microcavity via optical path transmission device 1, and laser 2 is modulated by an acousto-optic modulator and coupled into the same optical microcavity through optical matching lens; Two laser beams are split by a dichroic mirror, and the same-frequency resonant light signal reflected by the dichroic mirror is collected by a tuning fork sensor, while the light signal transmitted by the dichroic mirror is collected by a photodetector. The acquisition signals from the tuning fork sensor and photodetector are simultaneously acquired and demodulated to obtain mixed spectral data of methane and ethane gases. This data is then input into an artificial intelligence-based spectral analysis model, which outputs the independent spectra of methane and ethane after separation of the mixed spectral data.

8. The method for separating and identifying cross-interference between oil-type methane and ethane according to claim 7, characterized in that, The sawtooth wave and sine wave superposition signal is used to drive laser one to generate an emitted laser with a wavelength of 1.65 μm that absorbs the spectrum of methane gas; the single sawtooth wave signal is used to drive laser two to generate an emitted laser with a wavelength of 1.68 μm that absorbs the spectrum of ethane gas.

9. The method for separating and identifying cross-interference between oil-type methane and ethane according to claim 7, characterized in that, The spectral analysis model was trained through the following operations: Construct a dataset; obtain the absorption spectra of methane, ethane, and mixed gases under preset experimental conditions, and establish a spectral data simulation dataset by introducing system noise, which includes optical microcavity noise and detector noise; The constructed spectral data simulation dataset is divided into several subsets to train the spectral analysis model, and each subset is used as a validation set to adjust the hyperparameters in turn. The Adam optimizer is used to accelerate convergence. After all hyperparameters are determined, optimization is performed using the complete dataset. The mean absolute error of the spectra of the two spectra is used as the similarity evaluation index.

10. The method for laser monitoring and early warning of oil-type gas according to claim 9, characterized in that, The accuracy of separation is determined by a similarity evaluation index. If the similarity evaluation index is less than a preset threshold, then the independent spectra of methane and ethane are determined to be effectively separated. The formula for the similarity evaluation index is: ， In the formula, n is the number of spectral sampling points; and Representing the predicted spectrum and the true spectral value respectively. The value of each sampling point.

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