Continuous Real-Time Monitoring and Validation of Ambient H_2S to Odor Threshold Levels by Quantum Cascade Laser

摘要

The current challenges in continuously monitoring real-time ambient air excursions of hydrogen sulfide (H_2S) to odor level concentrations (« 100 ppbv) have been repeatedly demonstrated from ground level monitoring stations near landfills, chemical plants and oil/gas refineries, where the differentiation of real H2S emission hits from other sulfur containing pollutants has been problematic. The minimization of false positives and achieving adequate detection limits on a continuous basis are especially relevant given demanding odor-threshold regulatory limits of, for instance, ～60 ppbv H_2S averaged over three minutes and ～30 ppbv H_2S averaged over one hour. The usual combination of real-time analyzer instrumentation (fluorescence, optical tape and gold film analyzers) and air sample conditioning equipment (SO_2 converters) has led to questionable measurement results without the capability to fully speciate all the potential sulfur compounds and real-time quality assure the reported emissions. These types of analyzers make a strong case for an alternative non-intrusive optical monitoring system, as opposed to any type of air extractive chemical conversion and/or sensing system which often has sample integrity and mechanical limitations, to provide spectral information which can be validated.