Fe/Al-SiO_2复合金属氧化物用于燃煤烟气中汞的脱除

采用不同方法制备了Fe/Al-SiO_2复合金属氧化物以模拟赤泥成分,模拟烟气条件下考察其脱汞性能。结果表明,采用溶胶-凝胶法得到的复合金属氧化物在300-450℃具有优异的脱汞性能,其中,在350℃、3 h内平均脱汞率可达到94.8%。Fe_2O_3为Hg~0的氧化提供了晶格氧和化学吸附氧;SiO_2形成的硅溶胶则有利于活性组分Fe_2O_3的分散,增强了Hg~0与活性位的接触。基本模拟烟气中存在微量HCl和NO时,Hg~0脱除率接近100%;当烟气中存在0.2 mL/min、0.4 mL/min的SO_2时,吸附剂的平均脱汞率分别降至90.7%、53.4%,这主要是由于SO_2与Fe_2O_3反应生成Fe_2(SO_4)_3,导致了Fe_2O_3的失活并抑制汞的脱除。

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.