Development and Laboratory Investigations of a Denuder Sampling System for the Determination of Heavy Metal Species in Flue Gases at Elevated Temperatures

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Abstract
A denuder sampling system was developed to measure volatile metals at elevated temperatures. By using the denuder technique it is possible to avoid condensation and adsorption losses in the sampling line. To investigate the behavior of heavy metal species under different physical and chemical conditions, a laboratory scale quartz stack was built. Metal aerosol generators based on evaporation, diffusion and condensation are described. The diameter of the generated particles varied between 0.05–0.3 μm. The day to day reproducibility of the generation varied between 0.6-5.0% for chromium and 2.8–4.0% for cadmium (95% stat. significance). Denuders coated by elemental silver seem to be an efficient means for sampling of elemental Cd at 200°C. The diffusion coefficient of Cd was calculated from experimental data, and the value of (0.42±0.04) cm2/s was obtained. A detection limit of 0.2 μg/m3 for Cd determination can be reached by using a Ag-denuder, when a sampling time of 30 min and a flow rate of 60l/h is employed.

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