A portable laser-based sensor for detecting H2S in domestic natural gas

Abstract

Hydrogen sulfide (H2S) is a highly toxic gaseous component of natural gas that poses a significant hazard during the use of natural gas for domestic purposes; therefore, a high-sensitivity, on-line detection method is extremely important to ensure its safety for domestic use. In this work, a portable sensor was developed based on near-infrared tunable diode laser absorption spectroscopy (TDLAS). A special Herriott multipass cell (MPC) combined with a home-made embedded electronics system allowed for the fabrication of a compact sensor with a size of 50 × 20 × 10 cm3. A rugged movable cell was used for detecting contaminated gas samples. An embedded electronic system with a diameter of 8 cm was implemented to control the laser, acquire and process electronic signal. To reduce external interference, the calibration-free TDLAS (wavelength modulation frequency-2f/direct sine signal) was employed to suppress common field measurement noise. Based on the results of Allan deviation analysis, the limit of system detection could reach 0.14 ppm using the H2S absorption line at 6336.61 cm−1. It is suitable for on-line measurement because of its rapid response time. Its feasibility is validated for monitoring H2S in a domestic natural gas of pipeline. This work demonstrates a system for real-time and field measurement of H2S, which can be used to address the security risks associated with using natural gas.