Simple analyzer for continuous monitoring of sulfur dioxide in gas streams

The construction, optimization and use of simple and inexpensive gas analyzer for real time measurement of sulfur dioxide in gas streams are described The analyzer consisted of three main components (i) a custom fabricated hollow fiber membrane (HFM) gas contactor, (ii) carrier solution which absorbs SO(2) molecules from the gas stream in the HFM gas contactor and (in) a flow-through detector placed downstream which continuously measures the changes occurred to the carrier solution upon absorption of SO(2) molecules The significant acidic properties of the produced sulfurous acid suggested pH and conductivity detectors to monitor the decrease in pH or the increase in the conductivity which constituted the basis for quantification of SO(2) in the gas line Aqueous potassium oxalate (10(-1) mol/L) and hydrogen peroxide (10(-3) mol/L) were used as carrier solutions in combination with pH and conductivity detectors, respectively The analyzer equipped with pH detector provided linear potentiometric response to SO(2) concentration up to 1000 ppm with Nernstian slop of 61 mV/log[SO(2)] Excellent SO(2) recoveries (97-108%) were obtained in the presence of several folds of potentially interfering acidic gases, i e CO(2) and H(2)S The conductivity detector provided linear response up to 2500 ppm. Under optimized conditions, both detectors offered several favorable performance characteristics such as (i) fast response and recovery times, (ii) excellent signal stability and reproducibility (RSD = 0.5%), (iii) intrinsic high selectivity to most common neutral gases, e g, CH(4), N(2), O(2), CO, etc The suggested analyzer was applied successfully in monitoring the removal of SO(2) from SO(2)-N(2) gas mixtures with hollow fiber membrane contactor using distilled water or aqueous sodium hydroxide as stripping solvents. (C) 2009 Elsevier B V All rights reserved