Experimental study on the mechanism of mercury removal with Fe2O3 in the presence of halogens: Role of HCl and HBr

Experiments were conducted in a bench-scale fixed bed reactor with α-Fe 2 O 3 and γ-Fe 2 O 3 samples to investigate the mechanism of Hg 0 oxidation in the presence of HCl at 80–680   °C respectively. HCl is one of the main impurities in coal-derived fuel gas and its contribution to Hg 0 removal is complex and necessary to research. The experimental results showed that the Hg 0 removal mechanism with HCl could probably be divided into three stages based on the reaction temperature. At low temperature, the Eley–Rideal mechanism with HCl pre-adsorption was the most probable Hg 0 oxidation pathway. As the temperature increased more than 280   °C, Hg 0 removal efficiency differs significantly on α-Fe 2 O 3 and γ-Fe 2 O 3 , and the most suitable mechanism was Langmuir–Hinshelwood. With the increasing temperature to 680   °C, the homogeneous reaction between HCl and Hg 0 as well as Langmuir–Hinshelwood are responsible for the transformation of Hg 0 . We also discovered that the reaction time played a significant impact on the Hg 0 removal at low temperature, and caused the secondary mercury removal efficiency owing to the probable product of FeCl 3 . Additionally, HBr was adopted to compare with HCl, which obviously enhanced the Hg 0 oxidation on α-Fe 2 O 3 .