Methane (CH4), a kind of primary constituent of natural gas, is colorless and odorless. It can form explosive mixtures in coal mines and ambient air. That’s why scientists tried many ways to monitor whether the CH4 concentration reaches the lower explosive limit.
A research group from the Anhui Institute of Optics and Fine Mechanics (AIOFM) of the Hefei Institutes of Physical Science (HFIPS) took advantage of near-infrared spectroscopy and proposed a novel compact full range CH4 probe sensor using “trans-world” processing method, which marked the realization of full range detection.
“Common optical detection schemes cannot adapt to the dangerous site applications, and it will appear nonlinear at high concentrations,” said ZHANG Zhirong, who led the team. “This time we improved the detectable range and the detectable column density.”
In this research, the researchers encapsulated the circuit system and absorption cavity (optical path length 10 cm) together in a stainless-steel metal shell (4.7×3.5 cm). The gas concentration is directly output by the serial port, which is convenient for the layout and control of monitoring points in different applications. They also tested the performance of this microprobe in detail and verified the reliability and environmental adaptability of the probe system.
This newly developed detection scheme combines the benefits of calibration-free direct absorption spectroscopy (DAS) and the high-sensitivity wavelength modulation spectroscopy (WMS) for absolute concentration measurement according to the variation point, thereby ensuring the possibility of high accuracy of full-range detection.
“This probe sensor is highly integrated, full-range, compact, and low-cost,” said ZHANG Zhirong, “it’s is very suitable for leaking detection in nature gas industries and coal mines.”
Featured image: Photograph of the CH4 probe sensor. (a) Length of probe; (b) Diameter of probe; (c) Section and structure of the probe. (Image by ZHANG Lewen)
Provided by Chinese Academy of Sciences