CN-121994750-A - Multichannel methane dissipation monitoring method and device based on laser spectrum absorption

CN121994750ACN 121994750 ACN121994750 ACN 121994750ACN-121994750-A

Abstract

The invention provides a multichannel methane emission monitoring method and device based on laser spectrum absorption, which belong to the technical field of methane monitoring and comprise the steps of obtaining specific absorption wavelength of methane to laser, determining laser light source wavelength based on the wavelength, determining monitoring frequency, modulating the laser wavelength, carrying out multichannel photoelectric signal conversion, amplifying and denoising a multichannel electric signal obtained after conversion, extracting second harmonic of a multichannel methane gas absorption signal, denoising the extracted second harmonic through LabVIEW, respectively calling the denoised second harmonic data and standard data obtained after monitoring by MATLAB, carrying out iterative fitting on the second harmonic data and the standard data to obtain fitting coefficients, and inverting the multichannel methane gas concentration based on an inversion model. According to the method, the methane concentration data of a plurality of dissipation surfaces are obtained through multiple channels, so that the methane concentration monitoring of the large-range multi-dissipation surface continuity is realized, and the accuracy, reliability and continuity of the methane concentration monitoring are improved.

Inventors

SONG CHANGSHAN
LI WEI
HU XINYUN
SUN DONG
WANG XIAODONG
MA KUN
ZOU LIN
LIU CONG
YUE YU

Assignees

中国石油化工股份有限公司
中国石油化工股份有限公司胜利油田分公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (10)

1. A method for monitoring multi-channel methane emission based on laser spectral absorption, the method comprising: acquiring a specific absorption wavelength of methane to laser, and determining a laser light source wavelength based on the specific absorption wavelength; a plurality of monitoring points are distributed, monitoring frequency is determined, and real-time monitoring is carried out on the multi-channel methane dissipation condition according to the monitoring frequency; Modulating the laser wavelength through the set sine wave; Multichannel photoelectric signal conversion, namely converting a multichannel optical signal obtained after modulated laser passes through a methane gas area and is absorbed by multiple points into a multichannel electric signal through a photoelectric detector; Amplifying the multi-channel electric signal obtained after conversion by using a preamplifier, reducing noise of the amplified multi-channel electric signal by using a low-pass filter circuit, and extracting the second harmonic of a multi-channel methane gas absorption signal in the multi-channel electric signal by using a lock-in amplifier; and carrying out iteration fitting on the second harmonic data and the standard data to obtain fitting coefficients, and inverting the multichannel methane gas concentration based on an inversion model.
2. The method for monitoring the emission of multi-channel methane based on the absorption of laser spectrum according to claim 1, wherein the step of obtaining the specific absorption wavelength of methane to laser light and determining the laser light source based on the wavelength comprises the steps of: And obtaining specific absorption wavelength of the methane molecules according to the absorption characteristics of the methane molecules in a near infrared band and the absorption parameters of methane in the HITRAN database, and then determining the wavelength of the laser light source according to the obtained absorption wavelength.
3. The method for monitoring the emission of the multichannel methane based on the absorption of the laser spectrum according to claim 2, wherein the step of obtaining the specific absorption wavelength of the methane to the laser and the step of determining the laser source based on the specific absorption wavelength comprise the step of using the laser source with the wavelength of 1650 nm.
4. The method for monitoring the emission of the multichannel methane based on the absorption of the laser spectrum according to claim 1, wherein the modulating the wavelength of the laser by the set sine wave comprises modulating the wavelength of the laser by the sine wave with the frequency f=10 KHz and the peak-peak=110 mV.
5. The method for monitoring the multi-channel methane emission based on laser spectrum absorption according to claim 1, wherein the step of reducing the noise of the second harmonic of the extracted multi-channel methane gas absorption signal through LabVIEW, the step of calling the noise-reduced second harmonic data and standard data obtained through monitoring by using MATLAB respectively, and the step of performing iterative fitting on the second harmonic data and the standard data to obtain fitting coefficients, wherein the step of performing inversion model-based multi-channel methane gas concentration comprises the step of dynamically storing the noise-reduced second harmonic data after the second harmonic is reduced in LabVIEW.
6. The method for monitoring the multi-channel methane emission based on laser spectrum absorption according to claim 5, wherein the same depth processing is performed on the second harmonic data and the standard data by using MATLAB before iterative fitting is performed on the second harmonic data and the standard data.
7. The method of monitoring methane emissions in multiple channels based on laser spectral absorption of claim 1, wherein said obtaining a specific absorption wavelength of methane for laser light, determining a laser light source wavelength based on said wavelength comprises employing a DFB tunable laser light source.
8. The utility model provides a multichannel methane loss monitoring devices based on laser spectrum absorption, its characterized in that includes multichannel optical fiber methane monitor (1), a plurality of laser monitoring probe (2) and fiber cable (3), and each laser monitoring probe (2) is connected with connection methane monitor (1) respectively and utilizes fiber cable (3), multichannel optical fiber methane monitor (1) signal connection analysis processing module adopts the multichannel methane loss monitoring method based on laser spectrum absorption of any one of claims 1-7 to monitor, multichannel optical fiber methane monitor (1) draws the second harmonic of multichannel methane gas absorption signal, analysis processing module is used for LabVIEW to make an uproar and MATLAB data processing to the second harmonic of multichannel methane gas absorption signal.
9. The multi-channel methane emission monitoring device based on laser spectrum absorption according to claim 8, wherein the analysis processing module comprises a mobile workstation, a PC, a terminal server or a cloud server.
10. The multi-channel methane emission monitoring device based on laser spectral absorption according to claim 8, wherein the laser monitoring probe (2) comprises at least three.

Description

Multichannel methane dissipation monitoring method and device based on laser spectrum absorption Technical Field The invention relates to the technical field of methane gas monitoring, in particular to a multichannel methane emission monitoring method and device based on laser spectrum absorption. Background Methane is an important energy source that is used in many aspects of social development. However, there is a risk of leakage from the production, transportation to the utilization of methane through multiple nodes. Methane leakage and emissions not only affect the environment, cause climate change, but also waste resources and increase costs. Therefore, it is highly necessary to monitor methane. By monitoring the methane emission, the application and loss conditions of methane can be better known, leakage and emission problems can be found in time, corresponding measures are taken for maintenance and improvement, the resource waste is reduced, and the energy efficiency and the control cost are improved. Currently, single point monitoring techniques are commonly used to monitor emissions such as methane leakage and emissions. The single-point monitoring technology is focused on monitoring methane dissipation at a certain point, cannot monitor methane concentration change in a large range in real time, particularly limits coverage range and real-time performance of a large area or a mobile source, cannot provide comprehensive methane concentration distribution conditions, and can not monitor methane leakage when the methane leakage amount is small by adopting the single-point monitoring technology, and the error is large, so that the methane leakage can be missed. Disclosure of Invention Aiming at the problems, the invention provides a multichannel methane dissipation monitoring method and device based on laser spectrum absorption, which can comprehensively reflect the concentration change of methane in the surface of a large-area dissipation area in real time and reduce the probability of missing detection, the method has the advantages that the plurality of monitoring points are determined in the large-range area surface, the multichannel methane emission monitoring is carried out based on the laser spectrum absorption technology, the methane concentration data of the plurality of emission surfaces are acquired through multiple channels, the defect of single-point methane monitoring is effectively overcome, and the accuracy and the reliability of methane monitoring are improved. In one aspect, the present application provides a method for monitoring multichannel methane emission based on laser spectral absorption, the method comprising: acquiring a specific absorption wavelength of methane to laser, and determining a laser light source wavelength based on the specific absorption wavelength; a plurality of monitoring points are distributed, monitoring frequency is determined, and real-time monitoring is carried out on the multi-channel methane dissipation condition according to the monitoring frequency; Modulating the laser wavelength through the set sine wave; Multichannel photoelectric signal conversion, namely converting a multichannel optical signal obtained after modulated laser passes through a methane gas area and is absorbed by multiple points into a multichannel electric signal through a photoelectric detector; Amplifying the multi-channel electric signal obtained after conversion by using a preamplifier, reducing noise of the amplified multi-channel electric signal by using a low-pass filter circuit, and extracting the second harmonic of a multi-channel methane gas absorption signal in the multi-channel electric signal by using a lock-in amplifier; and carrying out iteration fitting on the second harmonic data and the standard data to obtain fitting coefficients, and inverting the multichannel methane gas concentration based on an inversion model. As a further improvement of the present application, the obtaining the specific absorption wavelength of methane to the laser light, and determining the laser light source based on the wavelength includes: And obtaining specific absorption wavelength of the methane molecules according to the absorption characteristics of the methane molecules in a near infrared band and the absorption parameters of methane in the HITRAN database, and then determining the wavelength of the laser light source according to the obtained absorption wavelength. As a further improvement of the present application, the obtaining the specific absorption wavelength of methane to the laser light, determining the laser light source based on the wavelength includes employing a laser light source having a wavelength of 1650 nm. As a further improvement of the present application, the modulating the laser wavelength by the set sine wave includes wavelength modulating the laser with a sine wave of frequency f=10 KHz, peak-to-peak=110 mV. As a further improvement of the application o