Development of iron-based sorbents for Hg 0 removal from coal derived fuel gas: Effect of hydrogen chloride

Abstract

Laboratory studies were conducted to develop an elemental mercury (Hg 0) removal process based on the reaction of H 2S and Hg 0 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 Hg 0 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 Hg 0 from coal derived fuel gases over iron-based sorbents such as iron oxide (Fe 2O 3), supported iron oxides on TiO 2, iron oxide–Ca(OH) 2, and iron sulfides were investigated. The Hg 0 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 (Fe 2O 3), the presence of HCl suppressed the Hg 0 removal rate. In the case of Fe 2O 3 (2 or 5 wt%)/TiO 2, the presence of HCl did not suppress the Hg 0 removal rate and the activity was stable. The Hg 0 removal performance of reagent FeS 2 was higher than that of the iron oxide, and not affected by the presence of HCl. The Hg 0 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 FeS 2 showed higher Hg 0 removal activity than that of FeS 2 ore. However, the Hg 0 removal performance of ground and kneaded FeS 2 ore was comparable to that of reagent FeS 2 probably due to the increase in porosity of the FeS 2 ore by grinding and kneading.