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Development of a Sub-ppb Resolution Methane Sensor Using a GaSb-Based DFB Diode Laser near 3270 nm for Fugitive
Jalal Norooz Oliaee1, Nicaulas A Sabourin2, Simon A Festa-Bianchet3
1Metrology Research Centre, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada.
ACS Sensors
|January 20, 2022
Summary
A new methane gas sensor offers high sensitivity and fast response for detecting fugitive emissions. Utilizing a novel wavelength-modulated spectroscopy approach, it achieves better than 1 ppbv sensitivity, ideal for mobile measurements.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Laser Spectroscopy
Background:
- Mobile measurement of fugitive methane emissions requires portable sensors with high sensitivity and fast response times.
- Existing technologies face challenges in simultaneously meeting both sensitivity and response time requirements for effective methane leak detection.
Purpose of the Study:
- To develop and characterize a novel methane gas sensor for mobile measurement of fugitive emissions.
- To evaluate different wavelength-modulated spectroscopy (WMS) metrics for sensor response linearity and sensitivity.
- To achieve a sensitivity better than 1 part per billion by volume (ppbv) for enhanced methane detection.
Main Methods:
- A GaSb-based distributed feedback diode laser emitting at 3.27 μm was used for methane detection in its ν3 vibrational band.
- Direct absorption spectra (DAS) and wavelength-modulated spectra (WMS) were recorded using a custom open-path multipass cell (6.8 m effective optical path length).
- A novel metrological approach characterized sensor response linearity using WMS metrics, including background-subtracted 1f-normalized quadrature signal (Q(2f/1f - 2f0/1f0)).
Main Results:
- The background-subtracted 1f-normalized quadrature signal (Q(2f/1f - 2f0/1f0)) exhibited the most linear response across calibration gas concentrations (1.5 to 40 ppmv).
- Direct absorption spectroscopy (DAS) fitting provided a traceable reference for sensor calibration.
- A sensitivity better than 1 ppbv was achieved in WMS mode with a 1-second integration time.
Conclusions:
- The developed methane gas sensor demonstrates high sensitivity and fast response times suitable for mobile fugitive emission monitoring.
- The novel WMS metric provides a robust and linear response for accurate methane concentration measurements.
- The sensor's performance meets the requirements for detecting ambient methane level enhancements from fugitive sources.
