Science Island team has made new progress in spectral line analysis of laser absorption spectrum gas measurement

Recently, Zhang Zhirong, a research team of Anguang Institute, Hefei Research Institute, Chinese Academy of Sciences, made new progress in the research of overlapping interference and separation of gas detection spectral lines with laser absorption spectroscopy (TDLAS), Relevant research achievements were published on internationally renowned journals Sensors and Actuaries B: Chemical and Optics Express under the titles of Research on CO and CH4 Aliasing Absorption Spectrum Demodulation Methods and Research on Aliasing Spectrum Demodulation Methods for Multi component Gas Measurement Based on Laser Absorption Spectrum Technology. The doctoral students Zhao Xiaohu and Wang Qianjin are the first authors of the article respectively.

Tunable semiconductor laser absorption spectroscopy (TDLAS) is the most commonly used gas detection method, which has the advantages of simple structure, fast response and easy operation. It has been widely used in environmental monitoring, medical diagnosis, industrial process monitoring and other fields. However, in special scenarios such as industry, coal mine, oil and gas, not only do the gas components contain very complex components, but also the content of gas components varies greatly, so that the laser absorption spectroscopy technology will encounter the aliasing of gas spectral lines during detection, resulting in a "common" technical bottleneck of cross interference, which increases the difficulty for the application of TDLAS technology and limits the application and development of this technology in some industries.

Zhang Zhirong's team, Sun Pengshuai, associate researcher, Zhao Xiaohu, and Wang Qianjin, two doctoral students, analyzed methane (CH4) and trace carbon monoxide (CO) in the coal mine, and solved the demodulation problem of mixing spectral interference of CH4 with the content of percentile and CO with the content of millions of components by using partial least squares and non negative least squares methods respectively. The concept of "spectral resolution" is put forward from the mechanism of absorption spectrum, and detailed simulation and complex experimental verification are carried out. Through experimental analysis, both methods have shown good demodulation effects, and can accurately demodulate the trace gas components in the special case that the concentration of two gases is 3 to 4 orders of magnitude different (the spectral characteristics are seriously aliased), greatly improving the selectivity and reliability of the system. Therefore, this method can demodulate the aliasing spectrum by software algorithm without adding hardware devices such as pressure control, which provides a direction for the accurate measurement of the concentration of two or more mixed gases using a single DFB laser, and broadens the environmental applicability and application prospects of the laser absorption spectrum gas sensing system.

The research was supported by the National Key R&D Plan, the National Natural Science Foundation of China, the Anhui Provincial Key R&D Plan, the "Spark" Fund of the Hefei Research Institute of the Chinese Academy of Sciences, and the key projects of the Bengbu Technology Transfer Center of the Chinese Academy of Sciences.

Second harmonic signals measured by CO and CH4 and mixture respectively

Treatment of the influence of CH4 gas with different concentrations on CO measurement results

Source: Hefei Institute of Material Science, Chinese Academy of Sciences