Abstract:

Combined removal with other coal fired pollutants was an effective method to control mercury emission during coal combustion.Accelerating the transformation of Hg⁰ to Hg²⁺ could enhance the performance of air pollution control devices in mercury emission control.Therefore, it is necessary to understand the influence factors of mercury speciation transformation.A bench scale test rig was built to simulate the process of mercury oxidation by gas components by using the Ontario Hydro Method for mercury detection at medium-to-low temperature.It was found that 90% Hg⁰ could be oxidized by Cl₂ at the concentration of 10 μl•L^-1.The process of Hg⁰ oxidation was sensitive within a range of SO₂ concentration, out of which SO₂ concentration had little influence on Hg⁰ oxidation.HCl, as the reaction product of H₂O and Cl₂, could also oxidize mercury from Hg⁰ to Hg²⁺, but its oxidation ability was weaker than Cl₂, which generally made H₂O an inhibitor of Hg⁰ oxidation.The process of NO₂ decomposition would release free oxygen atoms which could oxidize mercury from Hg⁰ to Hg²⁺, so mercury oxidation by NO₂ should be considered in a comprehensive kinetics model.

Key words:

燃煤烟气, 汞, 烟气组分, Hg形态, 形态转化

摘要：

与其他燃煤污染物联合脱除是解决燃煤汞排放问题的有效手段，促进Hg⁰向Hg²⁺的形态转化可以提高现有污染物控制装置对燃煤汞排放的控制能力。应用汞形态转化实验台，在中低温条件下研究分析Cl₂、SO₂、H₂O以及 NO₂对Hg⁰氧化过程的影响机理，结果表明，中低温条件下，10 μl•L^-1Cl₂可以氧化90%以上的Hg⁰。SO₂对Hg⁰形态转化过程的影响呈现区间性变化，按照SO₂浓度由小到大可划分为3个区间，只有在第（Ⅱ）区间内SO₂浓度才能显著影响Hg⁰的形态转化过程。H₂O与Cl₂反应的生成物HCl可以氧化Hg⁰，但其在中低温条件下氧化Hg⁰的能力弱于Cl₂，使得H₂O的存在抑制了Hg⁰的形态转化。将NO氧化为NO₂后进行脱除是低温条件下联合脱除的重要路线，NO₂在分解过程中释放出自由氧原子可以将Hg⁰氧化为HgO，这增强了低温条件下汞与NO_x联合脱除的技术可行性。

关键词:

燃煤烟气, 汞, 烟气组分, Hg形态, 形态转化