Effect Of Flue Gas Components On Hg-0 Oxidation And Adsorption By Modified Walnut Shell Coke In O-2/Co2 Atmosphere

Walnut shell was pyrolyzed and then impregnated with NH4Br to make sorbent for Hg-0 removal. The effect of flue gas components on Hg-0 removal performance was studied in O-2/CO2 atmosphere, and the results were compared with those in O-2/N-2 atmosphere. The mercury valence distribution during adsorption was obtained. NH4Br-modified walnut shell coke promoted Hg-0 removal, the Br-containing chemisorption site was a crucial factor. Although addition of CO2 did not introduce new oxygen-containing functional groups or change the mercury species, Hg-0 removal efficiency increased significantly. This may be because CO2 can increase the active sites on the carbon surface. In O-2/N-2 atmosphere, O-2 promoted formation of active center on the sorbent surface, which made Hg-0 more easily adsorbed and then reacted with Br-functional group to form more HgBr2. In O-2/CO2 atmosphere, O-2 promoted formation of some reactive carbon-oxygen complexes which acted as catalyst to facilitate Hg-0 oxidation and formation of HgO. NO improved removal of Hg-0, because the C & x2500;O functional group on the sorbent surface could catalyze the conversion of NO to NO2 in the adsorbed state and then formed Hg-2(NO3)(2). SO2 consumed oxygen on the sorbent surface and inhibited the Hg-0 removal.