The effect of selenite on mercury re-emission in smelting flue gas scrubbing system

Abstract

Recently, the mercury re-emission from the scrubbing solution has become a hot topic in wet flue gas desulfurization process (WFGD). Selenite is one of the most important matters in the solution. It is discovered that selenite have great effect on the mercury re-emission in the WFGD process in this paper. Several important parameters, such as selenite concentration, pH value, temperature and chloride concentration, and reaction mechanisms were studied on the Hg0 re-emission. The experimental results indicate that mercury reduction and re-emission can be effectively inhibited with high selenite and chloride concentrations, low temperature and pH value. The mechanisms for inhibition of mercury reduction and re-emission are proved to be different under acid and alkaline conditions respectively. Under acid condition, it is the formation of stable HgSe that decrease Hg0 re-emission. However, the formation of more stable HgSeO3SO32- or Hg(SeO3)22- than Hg(SO3)22- contributes to avoid the oxidized mercury reduction by sulfite ions and then the mercury re-emission under the alkaline condition. In addition, it is also found that Cl- ions can further enhance the inhibition effect and suppress Hg0 re-emission by the formation of stable HgSeO3Cl- and HgSeO3Cl22- complexes.