SULFUR-DIOXIDE ADSORPTION OVER ACTIVATED LIGNITE CHAR PREPARED FROM FLUIDIZED-BED PYROLYSIS

Abstract

Gravimetric analysis was carried out to investigate the relationship between SO2 adsorption capacity and pyrolysis conditions for chars prepared from fluidized bed pyrolysis of lignite at various conditions. It was found that pyrolysis temperature was the primary variable affecting SO2 adsorption capacity of chars while effects of steam and oxygen concentration in the fluidizing gas were not significant within the range of experimental conditions. The maximum SO2 adsorption capacity of chars was observed at the pyrolysis temperature of about 700 degrees C. This can be attributed to oxygen functional groups on carbons which are believed to adsorb SO2 through oxidation. Paucity of them can lead to poor SO2 adsorption capacity of carbons. However, too many of them per unit surface area is expected to hinder the adsorption through repulsive interactions of adsorbed SO2 present in the adsorbed multilayer. Therefore there exists an optimal amount of oxygen-functional groups on the carbon surface for the maximum SO2 adsorption capacity.