SELENIUM CAPTURE USING SORBENT POWDERS - MECHANISM OF SORPTION BY HYDRATED LIME

This study investigates the potential of mineral sorbents to capture s elenium which is sufficiently volatile to occur in the flue gas in vap or state. The sorption studies are conducted in a high-temperature rea ctor using SeO2 as the source of selenium. In both high (800-1000 degr ees C) and medium-temperature (400-700 degrees C) range, hydrated lime exhibits superior selenium sorption capability compared to other sorb ent powders. The results show that the mechanism of capture by Ca(OH)( 2) is not a simple physical adsorption process but seems to involve a chemical reaction between CaO and SeO2. The medium temperature range o f 400-600 degrees C is favorable for the reaction to occur and leads t o high selenium sorption. At higher temperatures, thermodynamic equili brium aids dissociation of the reaction product, and the amount of met al capture reduces drastically with increasing temperature. XRD studie s further confirm that calcium selenite is the dominant reaction produ ct.