Abstract
The implementation of a sensitive and selective as well as industrial fit gas sensor prototype based on wavelength modulation spectroscopy with second harmonic detection (2f-WMS) employing an 8-μm continuous-wave distributed feedback quantum cascade laser (CW-DFB-QCL) for monitoring hydrogen sulfide (H2S) at sub-ppm levels is reported. Regarding the applicability for analytical and industrial process purposes aimed at petrochemical environments, a synthetic methane (CH4) matrix of up to 1000 ppmv together with a varying H2S content was chosen as the model environment for the laboratory-based performance evaluation performed at TU Wien. A noise-equivalent absorption sensitivity (NEAS) for H2S targeting the absorption line at 1247.2 cm−1 was found to be 8.419 × 10−10 cm−1 Hz−1/2, and a limit of detection (LOD) of 150 ppbv H2S could be achieved. The sensor prototype was then deployed for on-site measurements at the petrochemical research hydrogenation platform of the industrial partner OMV AG. In order to meet the company’s on-site safety regulations, the H2S sensor platform was installed in an industry rack and equipped with the required safety infrastructure for protected operation in hazardous and explosive environments. The work reports the suitability of the sensor prototype for simultaneous monitoring of H2S and CH4 content in the process streams of a research hydrodesulfurization (HDS) unit. Concentration readings were obtained every 15 s and revealed process dynamics not observed previously.
Highlights
Sensitive and selective detection of hydrogen sulfide (H2S) is essential for production control and environmental monitoring purposes in the field of petrochemical, paper and pulp, or biotechnological processes
HDS is a catalytic process by which sulfur-containing impurities are removed from crude petroleum feedstocks and fuels during hydrogen exposition in the presence of cobalt-promoted molybdenum (CoMo) or nickel-promoted molybdenum (NiMo) catalysts and formation of H2S [4]
A sensitive, selective, and industrial fit gas sensor setup based on second harmonic wavelength modulation spectroscopy (2f-WMS) employing an 8-μm continuous-wave distributed feedback quantum cascade laser (CWDFB-QCL) was developed and implemented for detecting H2S at sub-ppm levels in petrochemical process gas streams
Summary
Sensitive and selective detection of hydrogen sulfide (H2S) is essential for production control and environmental monitoring purposes in the field of petrochemical, paper and pulp, or biotechnological processes. Since its first operational demonstration in 1994 [6], the quantum cascade laser (QCL) advanced to a powerful and reliable spectroscopic source of coherent light covering the mid-infrared (MIR) and terahertz spectral region for sensitive detection of molecular species on their fundamental vibrational bands and rendered laser-based absorption spectroscopy a powerful tool for industrial gas sensing [6,7,8,9]. A sensitive, selective, and industrial fit gas sensor setup based on second harmonic wavelength modulation spectroscopy (2f-WMS) employing an 8-μm continuous-wave distributed feedback quantum cascade laser (CWDFB-QCL) was developed and implemented for detecting H2S at sub-ppm levels in petrochemical process gas streams. On-site tests of the sensor were performed at the research hydrogenation platform of OMV AG
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