化学链燃烧钴基载氧体炉内脱汞机理研究

煤化学链燃烧炉内脱汞对降低煤燃烧单质汞的排放有重要意义，但是汞在载氧体作用下的氧化机制尚不明确。本文采用Co3O4载氧体在固定床反应器中进行脱汞实验，并在线检测反应器出口Hg0浓度。通过热力学计算揭示Hg0的催化氧化机制。实验结果表明，HCl与Co3O4的异相反应和HCl与Hg0的均相反应对Hg0脱除效率贡献都很大。随着Co3O4还原程度的增加，其对Hg0脱除效率急剧下降。计算结果表明，Hg0的氧化存在3种反应路径：Hg0与Cl2反应生成HgCl2；Hg0与Cl反应形成HgCl，然后被Cl/Cl2氧化形成HgCl2；Hg0与O反应生成HgO，HgO与Cl2O反应生成HgCl2。不同含Cl组分对Hg0氧化的贡献率顺序为：Cl2>Cl>CoCl3。本研究揭示炉内Hg0氧化机制对炉内脱汞技术的开发和应用有重要意义。

Reaction mechanism of mercury removal by cobalt-based oxygen carrier for chemical looping combustion

Mercury removal during chemical looping combustion for coal is important in reducing elemental mercury emission. However, the oxidation mechanism of elemental mercury by oxygen carriers is still unclear. Mercury removal experiments were carried out in a fixed bed reactor using Co₃O₄ as the oxygen carrier, with online measurement of Hg⁰ concentration at the outlet of the reactor. Hg⁰ catalytic oxidation mechanism was also revealed through thermodynamic calculation. Experimental results show that both the homogeneous reaction between HCl and Hg⁰, and the heterogeneous reaction between HCl and Co₃O₄ contribute significantly to Hg⁰ removal. With the reduction of Co₃O₄, the removal efficiency on Hg⁰ drops dramatically. Calculation results show that three reaction routes exist for Hg⁰ oxidation: the reaction between HCl and Co₃O₄ produces Cl, Cl₂, and CoCl₃, which then reacts with Hg⁰ to form HgCl₂; Hg⁰ reacts with Cl and CoCl to form HgCl, which is then oxidized by Cl, Cl₂, and CoCl₃ to form HgCl₂; Hg⁰ reacts with lattice oxygen to form HgO, which then reacts with HCl to form HgCl₂. Overall, the contributions of different Cl-containing components for Hg⁰ oxidation follow the sequence of Cl₂ > Cl > CoCl₃. This attempt reveals the Hg⁰ oxidation in a furnace and sheds light on the development and application of Hg⁰ removal technology.