Demonstration of a new on-line analyzer for the measurement of vaporized toxic metal compounds in a fluidized bed combustor

In this work we have demonstrated the applicability of a new on-line analyzer to the measurement of vaporized toxic metals, cadmium, and lead, at severe process conditions. The demonstrations were carried out in a bench-scale bubbling fluidized bed combustor during cocombustion tests of biomass and waste fuels. A continuous flow of sample gas is extracted into the analyzer, where it is mixed into the hot plasma jet resulting in substantial atomization of vapor phase and aerosol toxic metal compounds. Atom concentration is measured by atomic absorption spectroscopy with the aid of Zeeman background correction, and finally, the metal concentration in the sample gas is calculated. Analysis is made directly from a hot, wet, and particulate-laden sample gas. A part of the measurements were made at the outlet of the hot cyclone at the temperature of approximately 550 C, and another part was made directly from the combustion chamber, where temperature was 880 C. In both cases the measurements were successful and produced new data of cadmium and lead concentrations in hot flue gases. The results were compared with other analysis results, and a rather good agreement was obtained.