Removal of elemental mercury from flue gas using the magnetic Fe-containing carbon prepared from the sludge flocculated with ferrous sulfate

Wang, Yuan; Li, Honghu; He, Zhong; Zhang, Meng; Guan, Jianmin; Qian, Kaikai; Xu, Jingjie; Hu, Jiangjun

Removal of elemental mercury from flue gas using the magnetic Fe-containing carbon prepared from the sludge flocculated with ferrous sulfate

2020

The sewage sludge flocculated with ferrous sulfate (SFS) was prepared by one-step pyrolysis to obtain magnetic Fe-containing carbon. Results showed that only a small amount of FeₓOy as well as extremely weak magnetism were observed at pyrolysis temperatures of less than 500 °C. SFS tended to exhibit intensive agglomeration, leading to the drastic increase of the crystalline-phase particle size at high pyrolysis temperature. The optimal pyrolysis temperature is 700 °C, corresponding to the production of some sulfides, an optimal content of FeₓOy, and a suitable BET surface. Hg⁰ removal efficiency of SFS700 (SFS pyrolyzed at 700 °C) reached 80.7% at the reaction temperature of 125 °C. The presence of O₂ and low concentration of SO₂ enhanced the Hg⁰ removal, while the H₂O vapor and high SO₂ concentration inhibited it. Meanwhile, good resistance for the adsorbent to moderate concentrations of SO₂ and H₂O was observed. Moreover, the good magnetism performance is conducive to the recovery and utilization of the SFS700 in flue gas. Therefore, SFS can be used for Hg⁰ removal without any chemical modification after undergoing one-step pyrolysis and this study has guiding significance for the resource utilization and engineering practices.

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