燃煤烟气中的痕量元素单质汞是我国大气中主要的汞排放源之一，如何实现燃煤烟气中单质汞的高效脱除是关注重点和研究热点。前期众多学者研究了不同组分、浓度、温度和空速等对现有装置协同脱汞、催化剂氧化、等离子体氧化、光催化氧化、自由基氧化以及吸附剂等的脱汞效果和反应机理。由于烟气组分SO2和H2O对活性位的竞争、吸附剂吸附容量低和二次产物污染等难题，在应用上仍存在瓶颈。系统介绍了现阶段单质汞捕获的不同方式和特点以及现阶段脱汞进展，从降低H2O和SO2的脱汞毒害性、确定反应温度、获得稳定的脱汞化合物、探索安全简便的样品制备方法及实现活性位官能团的定向负载4个方面进行总结，重点分析了催化剂和吸附剂在脱汞过程中的特点，讨论了喷射脱汞过程中吸附剂的影响因素和传质过程。结果表明，硫活性位的负载可有效克服烟气中SO2的影响；甲基基团和特定结构可使吸附剂具有高疏水特征；具有适宜的孔隙结构和具有一定层间距的吸附剂，可克服传质扩散步骤的限制从而提高除汞性能。烟气中实际条件如流场和物理化学反应等，是影响流体与吸附剂界面反应和反应活性的关键步骤，影响吸附剂的应用效果。实验室试验、动力学模型和密度泛函理论反映了限制因素、迁移路径、参数设置等对单质汞脱除的影响，如对气态单质汞在缺陷表面和完整表面的吸附构型和迁移路径等分析可揭示单质汞的吸附过程。在分离再生方面，金属铁等金属类氧化物的引入可改善吸附剂的分离问题，对现有吸附剂的喷射应用效果、应用影响因素和吸附剂的再生方式等进行了对比；再生效果和再生温度高是再生环节面临的问题。吸附剂主要通过热处理过程实现再生，再生温度300～500 ℃、再生时间30～180 min即可实现较高脱汞效率，再生过程主要通过相应活性位的补充和官能团的转变实现。最后对催化剂和吸附剂存在的瓶颈、挑战和优化方向进行了展望，为单质汞防治的工业化应用提供参考。

Trace elemental mercury in flue gas of coal burning is one of the main atmospheric mercury emission sources in China. How to achieve efficient removal of elemental mercury in flue gas of coal burning is the focus of attention and research in China. Previously, scholars have conducted in-depth studies on the effectiveness and reaction mechanism of existing devices for co-dehumidification, catalyst oxidation, plasma oxidation, photocatalytic oxidation, free radical oxidation and adsorbent in terms of different reaction components, reaction concentrations, reaction temperatures and reaction air velocities. However, the practical application of elemental mercury still faces many bottlenecks due to the obstacles of competition caused by the competition of flue gas components of SO2 and H2O for active sites, low adsorption capacity and secondary waste pollution. This study systematically introduced the different ways and characteristics of elemental mercury capture at present and focused on analyzing the influence of different experimental conditions on the application of catalysts and adsorbents in mercury removal. The progress of the present stage of mercury removal was summarized, including how to overcome the mercury removal toxicity of H2O and SO2, select the appropriate reaction temperature, obtain stable mercury removal compounds, explore safe and simple sample preparation methods, and realize the directional loading of functional groups at active sites. The results show that the loading of sulfur active sites can effectively resist the influence of SO2 in flue gas. Methyl groups and specific structures can make the adsorbent have high hydrophobic characteristics. Suitable pore structure and adsorbents with certain layer spacing can improve the performance of mercury removal by overcoming the limitation of the mass transfer diffusion step. The actual conditions in flue gas, such as flow field and physical-chemical reactions, affect the time evolution and internal evolution of fluid mass transfer to deviate from the standard, and influence the practical application of the adsorbent. The experimental effect analysis, kinetic analysis model and density functional theory reflect the influence of the limiting factors of elemental mercury removal, migration path and the influence of external reaction parameters and internal structure. The analysis of the adsorption configuration and migration paths of gaseous singlet mercury on defective and intact surfaces, for example, can reveal the adsorption process of singlet mercury. In terms of separation and regeneration, the actual spray application of the existing adsorbents, the influencing factors and the regeneration mode of the adsorbents were compared. It is found that the introduction of metals or metal-like oxides can improve the separation problem of adsorbents and the regeneration effect and the high regeneration temperature are the problems faced in the regeneration process. The adsorbent is generally regenerated by heat treatment. The regeneration temperature of heat treatment is 300-500 ℃, and the regeneration time is generally 30-180 min, which can achieve high mercury removal efficiency. The regeneration is realized by supplementing the corresponding active sites and functional groups. Finally, the bottleneck, challenge and optimization direction of catalysts and adsorbents were prospected, which can provide reference for the industrial application of elemental mercury control.

0 引言

1 研究背景

2 现有单质汞脱除手段

   2.1 现有设备协同脱除

   2.2 催化剂氧化

   2.3 等离子体氧化

   2.4 光催化氧化

   2.5 自由基氧化

   2.6 吸附剂

3 单质汞脱除的影响因素

   3.1 反应气氛的影响

   3.2 汞初始浓度的影响

   3.3 反应温度的影响

   3.4 反应空速的影响

4 单质汞脱除机理及应用再生

   4.1 脱汞机理

   4.2 吸附剂喷射应用

   4.3 吸附剂再生

5 结语与展望