Characteristics and inhibition of mercury re-emission from desulfurization slurry by Fenton reagent

In this paper, the mercury re-emission from desulfurization slurry and mercury distribution in gas-liquid-solid three-phase at different desulfurization slurry parameters were studied. Besides, the inhibition performance of Fenton reagent for mercury re-emission and distribution was also investigated. The results show that the Hg 0 would re-emit from desulfurization slurry, and the proportions of mercury in gas-liquid-solid three-phase were about 12.17%, 77.72% and 12.08% at typical desulfurization slurry parameter. The S(IV) concentration (sulfite and/or bisulfite concentration), temperature and pH value of desulfurization slurry had great impacts on mercury re-emission and distribution. The increase of S(IV) concentration weakened the mercury re-emission, increased the proportions of mercury in solid phase and liquid phase. The increase of slurry temperature could intensify the mercury re-emission, increase the proportion of mercury in solid phase, but decrease the proportion of mercury in liquid phase. Higher pH value was favorable for the weakening of mercury re-emission, but would increase the proportion of mercury in solid phase and liquid phase. Moreover, the introduction of Fenton reagent into desulfurization slurry could inhibit the mercury re-emission and some mercury that should be re-emitted before would be restrained in solid phase, leading a slight increase of proportion of mercury in solid phase. The existing of oxygenated free radicals , which were generated from Fenton reagent, was the main reason for the inhibition of mercury re-emission. The increase of Fe 2+ and H 2 O 2 concentration was conducive to the promotion of inhibition performance, but the effect gradually to weaken. The appropriate value of Fe 2+ concentration was 0.04 mM with the H 2 O 2 concentration of 0.30 mM in experiments. In addition, the better inhibition performance (about 80%) of Fenton reagent for mercury re-emission would be realized at lower S(IV) concentration (1–5 mM), lower temperature (30–40 °C) and lower pH value (4.0–5.0) of slurry.