Cerium-doped activated carbon with high dispersions of cerium and sulfur species was successfully synthesized by an in situ ion exchange method. A high space velocity was employed to differentiate the mercury removal performance of cerium-doped activated carbon with (Ce/AC) and without (Ce/C) activation in simulated flue gases , at 80 to 150 °C. The Ce/AC showed much higher mercury removal ability than those of Ce/C, commercial coconut AC and NH 4 Cl modified AC. The main mercury species formed over spent Ce/AC were HgO, HgS and HgSO 4 . The HgO was formed mainly through the oxidation of mercury by lattice oxygen, while the HgS was generated by the reaction between Ce 2 S 3 and mercury. The formation of HgSO 4 might be due to the reaction of mercury with SO 2 and/or Ce 2 S 3 with the aid of oxygen. The Ce/AC showed impressive regeneration and reuse ability, the mercury removal performance of which showed no obvious change even after 5 runs of regeneration. The mercury species formed over Ce/AC also had no obvious change after regeneration; however, the Ce 2 S 3 over Ce/AC was converted to CeO 2 after regeneration. With the above excellent properties, Ce/AC may prove to be an advantageous alternative to commercial AC for mercury removal in power plants.
The introduction of additives into desulfurization slurry may inhibit the mercury re-emission from slurry and improve the stabilization of mercury in slurry. In this paper, the effect of common additives, such as sodium sulfide (Na 2 S), 2,4,6-trimercaptotriazine trisodium (TMT-18), sodium dithiocarbamate (DTCR-2) and Fenton reagent, on mercury distribution in gas–liquid–solid phase was investigated under typical operating conditions. Meanwhile, the effect of different additive dosages on the inhibition performance of mercury re-emission was studied. Furthermore, the inhibition mechanisms of different additives were also discussed. The experimental results showed that Na 2 S, TMT-18, DTCR-2 and Fenton reagent could inhibit the mercury re-emission from desulfurization slurry and some mercury that might reemit into the gas phase before would be restrained in the solid phase. For additives such as Na 2 S, TMT-18 and DTCR-2, with the increase in additive dosages, the inhibition performances of mercury re-emission were improved, but the enhancing effects tended to level off. More mercury could be restrained in the solid phase by forming HgS, Hg-TMT and Hg-DTCR. However, for additives such as Fenton reagent, the inhibition performance of mercury re-emission was first increased and then decreased with the proportion of Fe 2+ and H 2 O 2 in Fenton reagent increasing. There existed an optimal proportion. The oxygenated free radical generated by Fenton reagent with Fe 2+ as catalysis was the main reason for the inhibition of mercury re-emission, and more mercury would be oxidized and then restrained in solid phase due to the formation of HgSO 4 and Fe(OH) 3 .
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