Analyzer for continuous monitoring of H2S in gas streams based on a novel thermometric detection

Development, characterization, and application of a novel gas analyzer for continuous monitoring for hydrogen sulfide (H2S) in gas streams are presented. The principle of operation is based on absorbing H2S from the analyte gas stream into aqueous sodium hydroxide solution flowing through a custom-made hollow fiber membrane (HFM) contactor (diffusion scrubber). The stripped sulfide ions in the alkaline solution are oxidized in line with hydrogen peroxide solution. The redox reaction is significantly exothermic and the temperature rise (ΔT) of the flowing mixed reagent stream is measured and proved as useful novel analytical signal for the quantification of H2S. The analyzer exhibited linear response to H2S concentrations for at least two orders of magnitude, i.e., 0.05–5.0% (r2 = 0.9996). The analyzer exhibited excellent selectivity in the presence of several common gases such as CO2, CO, CH4, O2 and N2 whereas SO2 exerts positive interference (∼22%). The analyzer exhibited excellent signal repeatability (CV < 1%), excellent signal stability (2 h at least) and acceptable response time (t95%) of 7 min. In addition to the favorable performance characteristics, the presented analyzer offers several other advantages such as long operational life time, conveniently tuned sensitivity, low cost of construction and operation; (iv) short setup time, and (v) high reliability. The analyzer was successfully applied in monitoring the removal of H2S from gas stream using a lab scale setup.