Effect of atmosphere of SO2 coexisted with oxidizing gas on mercury removal under oxy-fuel condition

The effects of oxidizing gas and SO2 in oxy-fuel combustion on mercury adsorption by modified corn stalk char were studied. Results showed that after 1% NH4Cl modification, the number of surface pores and oxygen-containing functional groups increased, which contributed to the improvement of adsorption capacity. O2 could promote the adsorption of mercury by heterogeneous oxidation and oxygen-containing functional groups. The addition of HCl could obviously improve the adsorption effect of adsorbent as the result of the chlorine-containing function groups on the surface of biomass char and the effect of Cl2 produced by Deakin reaction. SO2 could be oxidized to SO3 by oxygen atoms on the surface of adsorbent, which competed with the active sites and inhibited adsorption. SO2 could also directly react with Hg0 to produce HgSO4. The increase of O2 would alleviate the inhibition effect of SO2. SO2 could react with O2 by some ways and thus resulted in the decrease of oxidation rate owing to the consumption of O2. The existence of SO2 would weaken the oxidation effect under HCl through the reaction with Cl2 produced by HCl and O2, and SO2 would compete with HCl for the active sites on the surface of adsorbent.