Development, Characterization, and Applications of Portable Analyzer for Continuous Monitoring of H

A bench-scale analyzer for continuous monitoring of H 2 S in gas streams was previously described (Sensors & Actuators B 2012, 162, 377-383 ). This analyzer was based on the exothermic reaction between the scrubbed H2S, in alkaline solution, with hydrogen peroxide. The analyzer offered several advantages but suffered from relatively slow response time (i.e., 7 min) and relatively low sensitivity (Limit of Detection = 100 ppm). In the present work, a substantially improved detector design and direct mixing of the gas with the liquid reagents are descried. The improved detector was in the form of a coiled thin-walled stainless steel (SS) tube which acted also as a compartment for direct gas absorption and reaction with the sodium hydroxide and hydrogen peroxide reagents which eliminated the need for the gas scrubber based on microporous hollow fiber membranes. The average temperature of the SS coil was measured by two thermocouples attached to the outer surface of the coil with thermally conductive epoxy. The improved detector design and the simplified scheme proved very successful to achieve 6 times faster response (i.e., 70 s) and 20 times more sensitive response (i.e., 10 ppm) in gas stream and improved repeatability (CV = 0.55%). In addition, the previously reported advantages such as the excellent signal stability, wide dynamic range (up to 5% H 2 S) and convenient tuning the sensitivity and linearity by varying the ratio between the gas and reagents flow rates were perfectly retained. The improved detector was utilized to construct a compact portable version of the H2S analyzer (~ 6 kg) which provided a stand-alone operation of real time monitoring of H2S in gas stream for up to 4 hours prior to the need of reagents refill or battery re-charge. The application of the described portable analyzer in monitoring H2S removal from H2S-N2 gas stream using hollow fiber membrane contactor and absorption solvent, and in the determination of sulfide ions in liquid samples are also presented. A comparison between the response of the present portable H2S analyzer and a commercial analyzer is also presented.