Oxygen-Induced Elemental Mercury Oxidation in Chemical Looping Combustion of Coal

Qiuqi Liu; Dunyu Liu; Mingguo Ni; Kailong Xu; Jingjing Ma; Zhuang Liu; Jing Jin; Huancong Shi

doi:10.1021/acsomega.2c01709

Oxygen-Induced Elemental Mercury Oxidation in Chemical Looping Combustion of Coal

ACS Omega. 2022 Jun 6;7(24):20959-20967. doi: 10.1021/acsomega.2c01709. eCollection 2022 Jun 21.

Authors

Qiuqi Liu^{1

2}, Dunyu Liu^{1

2}, Mingguo Ni^{1

2}, Kailong Xu^{1

2}, Jingjing Ma³, Zhuang Liu^{1

2}, Jing Jin^{1

2}, Huancong Shi^{4

5}

Affiliations

¹ School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
² Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China.
³ State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, Ningxia 750021, China.
⁴ Huzhou Institute of Zhejiang University, Huzhou, Zhejiang 31300, China.
⁵ Environmental Science and Technology, University of Shanghai for Science and Technology, Shanghai 200093, China.

Abstract

Mercury emission is an important issue during chemical looping combustion (CLC) of coal. The aim of this work is to explore the effects of different flue gas components (e.g., HCl, NO, SO₂, and CO₂) on mercury transformation in the flue gas cooling process. A two-stage simulation method is used to reveal the reaction mechanism of these gases affecting elemental mercury (Hg⁰) oxidation. Furthermore, using this method, Hg⁰ oxidation by eight oxygen carriers (Co₃O₄, CaSO₄, CeO₂, Fe₂O₃, Al₂O₃, Mn₂O₃, SiO₂, and CuO) commonly used in CLC are investigated and their Hg⁰ oxidation efficiencies were compared with the existing experimental results. The results show that HCl, NO, and CO₂ promote Hg⁰ oxidation during flue gas cooling, while SO₂ inhibits Hg⁰ oxidation. The stronger the oxygen release capacity of oxygen carriers, the higher the oxidation efficiency of Hg⁰ becomes. The order of Hg⁰ removal efficiency from high to low is Co₃O₄, CuO, Mn₂O₃, CaSO₄, Fe₂O₃, CeO₂, Al₂O₃, and SiO₂, and this sequence is in good agreement with the existing experimental results. Different flue gas components directly or indirectly affect the O₂ content, thus affecting the content of gaseous oxidized mercury (Hg²⁺). Different oxygen carriers have different oxygen release capacities and different Hg⁰ oxidation efficiencies. Therefore, O₂ is the core species affecting the mercury transformation in CLC.