Removal of elemental mercury from flue gas by Fe/Al-SiO₂ complex

The Fe/Al-SiO₂ composite metal oxides were prepared by various methods to simulate the composition of red mud. A series of experiments were carried out to study the mercury removal performance from simulated flue gas. The results show that the composite metal oxide obtained by sol-gel method has an excellent mercury removal performance in a temperature range of 300-450 ℃. Among them, average mercury removal efficiency can reach 94.8% within 3 h at 350 ℃. Fe₂O₃ provides lattice oxygen and chemical adsorbed oxygen for the oxidation of Hg⁰, and SiO₂ is conducive to the dispersion of the active component Fe₂O₃, which enhances the contact between Hg⁰ and the active sites. In the presence of trace HCl and NO in flue gas, the removal efficiency of Hg⁰ is close to 100%. However, the average mercury removal efficiency reduces to 90.7% and 53.4% respectively after adding 0.2 mL/min and 0.4 mL/min SO₂, since the reaction of SO₂ and Fe₂O₃ produces Fe₂(SO₄)₃, leading to the deactivation of Fe₂O₃.