Multi-component gas remote sensing technology in petrochemical processes based on quantum cascade lasers

To address the challenge of non-contact fugitive emission monitoring for multi-component hazardous gases, such as H₂S, CH₄, and C₂H₂, throughout the entire petrochemical industry chain, a multi-component gas remote sensing technology based on mid-infrared quantum cascade lasers (QCL) and wavelength modulation spectroscopy was proposed in this paper. A QCL centered at 8.309 μm was employed to simultaneously scan the absorption spectra of H₂S, CH₄, and C₂H₂. By this approach, the difficulty of covering the absorption peaks of multiple gas components with a single light source while avoiding water vapor interference was successfully resolved. To verify the system's adaptability to industrial field conditions, a theoretical analysis based on the Phong reflection model and an experimental verification platform were established. Experimental results show that effective return signals could be acquired from the surfaces of typical non-cooperative targets, such as aluminum plates and epoxy resin, by which the feasibility of gas remote sensing on metal and coating surfaces is verified. Allan variance analysis indicated that the limits of detection (LOD) at the optimal integration time are 8.75×10⁻⁷ for H₂S, 5.792×10⁻⁶ for CH₄, and 2.4204×10⁻⁵ for C₂H₂. Furthermore, the system is found to exhibit excellent dynamic response capabilities, with a wavelength switching response time of less than 500 ms. By integrating high sensitivity, non-contact remote sensing, and rapid response, this technology is considered to provide robust technical support for safety monitoring in petrochemical processes.