Postcombustion Measures for Cleaner Solid Fuels Combustion:Activated Carbons for Toxic Pollutants Removal from Flue Gases

摘要

In this work the efficiency of postcombustion measures (i.e.,activated carbon utilization) to achieve cleaner solid fuels combustion was evaluated.Thus,two commercial activated carbons (Calgon F400 and RWE active coke) were tested for removing toxic polluting compounds (Hg,PCBs,PCDD/Fs) from the gas phase.The effects of the pore structure and surface chemistry of the activated carbons tested were investigated,along with the sorption temperature and sulfur addition in carbon matrix.Experiments were realized in a bench-scale adsorption unit and in a commercial solid fuels-fired hot water boiler.The results showed that both activated carbons tested are suitable for the removal of toxic compounds (i.e.,Hg,PCBs,PCDD/Fs) from the gas phase.Due to differences in Hg adsorptive capacity and adsorption rate,which are attributed to the diversified pore structure and surface chemistry of the activated carbons,RWE active coke is,presumably,more suitable for continuous Hg removal (i.e.,activated carbon injection),while Calgon F400 is more suitable for batch one (packed column).For both activated carbons,Hg adsorption capacity was reduced with temperature increase,while it was enhanced by the presence of sulfur.Oxygen surface functional groups seem to be involved in Hg deg adsorption mechanism.Lactones are believed to act as potential active sites for mercury adsorption,while phenols may act as inhibitors.The removal of PCBs and PCDD/Fs from the gas phase seems not to be a problem for the activated carbons tested,regardless of their pore structure or surface chemistry.