卤化钠浸渍赤泥脱除燃煤烟气中单质汞的研究

Removal of elemental mercury from coal combustion flue gas by sodium halides impregnated red mud

  • 摘要: 高效、低成本的燃煤烟气脱汞吸附剂仍是有害气体污染物控制的重要挑战。本研究制备了一系列卤化钠(NaBr 和 NaI)浸渍改性的赤泥基吸附剂,用于捕集模拟燃煤烟气中的元素汞(Hg0),并对改性赤泥进行了物理化学表征分析, 包括形貌特征, 晶体结构, 化学成分和热性能等。研究结果表明,卤化物浸渍对赤泥的比表面积和孔径有很大影响。在固定床反应器上,对改性赤泥在模拟烟气(含有 N2、O2、CO2、NO 和 SO2 等)中的脱汞性能进行了评估,在最佳吸附温度(160 °C)下, NaI 改性吸附剂(RMI5)对混合气体(包括 O2、NO 和 HCl)中的汞的脱除率达到 98%。此外, 动力学研究中发现, 伪二阶模型拟合结果证明了吸附 Hg0 的化学吸附机理。

     

    Abstract: Mercury removal from coal combustion flue gas remains a significant challenge for environmental protection due to the lack of cost-effective sorbents. In this study, a series of red mud (RM)-based sorbents impregnated with sodium halides (NaBr and NaI) are presented to capture elemental mercury (Hg0) from flue gas. The modified RM underwent comprehensive characterization, including analysis of its textural qualities, crystal structure, chemical composition, and thermal properties. The results indicate that the halide impregnation substantially impacts the surface area and pore size of the RM. Hg0 removal performance was evaluated on a fixed-bed reactor in simulated flue gas (consisting of N2, O2, CO2, NO and SO2, etc.) on a modified RM. At an optimal adsorption temperature of 160 °C, NaI-modified sorbent (RMI5) offers a removal efficiency of 98% in a mixture of gas, including O2, NO and HCl. Furthermore, pseudo-second-order model fitting results demonstrate the chemisorption mechanism for the adsorption of Hg0 in kinetic investigations.

     

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