A Closed Optical Path Trace H2S Sensing System Based on Vacuum Ultraviolet Differential Absorption Spectroscopy Combined with Reconstructed Domain Point Cloud Segmentation

Accurate detection of trace hydrogen sulfide (H2S) plays an indispensable role in the fields of industrial emission reduction and power troubleshooting. In view of the oscillatory absorption characteristics of H2S in the 185-210 nm band, ultraviolet differential optical absorption spectroscopy (UV-DOAS) has been recognized as a promising technique for measuring H2S concentrations. However, spectral overlap caused by the presence of oxygen (O2) in the open optical path and in the mixture, along with the irregular absorption characteristics of H2S, makes it challenging to assess trace H2S concentrations using the vacuum ultraviolet band. In this study, we propose a closed optical path H2S sensing system based on vacuum ultraviolet absorption spectroscopy combined with reconstructed domain point cloud segmentation. First, a closed optical path structure is used to eliminate O2 present in the optical path gaps. Then we present a spectral line analysis method based on sinusoidal spectral reconstruction (SSR) combined with point cloud segmentation. This approach effectively eliminates spectral interference of O2 on H2S spectra within the reconstructed domain. Finally, the irregular absorption features of H2S are organized to facilitate the accurate measurement of H2S at low concentrations. Results reveal that the sensing system can measure H2S dynamically at low concentrations using the vacuum ultraviolet band, with a mean relative error (MRE) of 1.61%. Meanwhile, the detection limit for H2S reached 41.2 ppb at a detection time of 100 s. To the best of our knowledge, this is the best level of H2S measurement for direct application of UV-DOAS technology.