Development of iron-based sorbents for Hg0 removal from coal derived fuel gas: Effect of hydrogen chloride

Laboratory studies were conducted to develop an elemental mercury (Hg0) removal process based on the reaction of H2S and Hg0 using iron-based sorbents for coal derived fuel gas. It is well known that hydrogen chloride (HCl) is present in fuel gases derived from some types of coal, but the effect of HCl on the Hg0 removal performance of iron-based sorbents in coal derived fuel gas is not yet well understood. In this study, the effects of HCl on the removal of Hg0 from coal derived fuel gases over iron-based sorbents such as iron oxide (Fe2O3), supported iron oxides on TiO2, iron oxide–Ca(OH)2, and iron sulfides were investigated. The Hg0 removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80 °C using simulated fuel gas. In the case of iron oxide (Fe2O3), the presence of HCl suppressed the Hg0 removal rate. In the case of Fe2O3 (2 or 5 wt%)/TiO2, the presence of HCl did not suppress the Hg0 removal rate and the activity was stable. The Hg0 removal performance of reagent FeS2 was higher than that of the iron oxide, and not affected by the presence of HCl. The Hg0 removal rate of iron oxide–Ca(OH)2 was not effected by the presence of HCl, because HCl was captured by Ca(OH)2. The reagent FeS2 showed higher Hg0 removal activity than that of FeS2 ore. However, the Hg0 removal performance of ground and kneaded FeS2 ore was comparable to that of reagent FeS2 probably due to the increase in porosity of the FeS2 ore by grinding and kneading.