Impact of flue gas conditions on mercury uptake by sulfur-impregnated activated carbon

Novel sulfur-impregnated activated carbons (SIACs) have shown excellent mercury uptake capacity when pure nitrogen was used as a carrier gas. This study investigated the impact of various gas constituents found in a real flue gas on the performance of SIACs. Fixed-bed adsorber tests showed that CO2 (up to 15%) had no impact on mercury uptake by SIAC, while the presence of O-2 (up to 9%) increased the adsorptive capacity up to 30%. Increase in the amount of oxygen-containing acidic surface functional groups had no impact on mercury uptake, and it is postulated that the enhanced performance was due to the formation of HgO catalyzed by SIAC. Moisture presence (up to 10%) can decrease SIAC's capacity for mercury uptake by as much as 25% due to competitive adsorption and additional internal mass transfer resistance. SO2 (1600 ppm) and NO (500 ppm) exhibited no impact on mercury uptake by SIAC even in the presence of 10% moisture. Adsorptive capacity of SIAC decreased significantly when the reaction temperature increased from 140 to 250 and 400 degrees C due to the pronounced exothermic nature of HgS formation, but increasing the empty-bed contact time can partially offset this loss of capacity.