Effect of additives on stabilization and inhibition of mercury re-emission in simulated desulphurization slurry

Abstract

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 (Na2S), 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 Na2S, 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 Na2S, 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 Fe2+ and H2O2 in Fenton reagent increasing. There existed an optimal proportion. The oxygenated free radical generated by Fenton reagent with Fe2+ 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 HgSO4 and Fe(OH)3.