NH4Cl改性活性炭脱除气态Hg0的特性分析

制备了原始活性炭与NH₄Cl改性活性炭，对其进行了物化特性表征，在固定床汞吸附实验台上考察了N₂气氛下颗粒粒径、NH₄Cl溶液浓度、SO₂、CO₂等因素对活性炭脱除Hg⁰性能的影响。研究结果表明：NH₄Cl浸渍改性没有造成活性炭孔隙结构的明显变化，但使得Cl元素成功担载到活性炭表面；随着颗粒粒径增大，活性炭吸附Hg⁰的外部传质速率、内部扩散速率均降低，较小的颗粒粒径有利于活性炭脱汞；由NH₄Cl改性在活性炭表面所产生的卤素官能团（AC-Cl）能够有效地氧化烟气中的Hg⁰，增强了活性炭对于Hg⁰的氧化吸附作用；SO₂能有限地促进原始活性炭的脱汞性能，对NH₄Cl改性活性炭脱汞性能则表现出先促进后抑制并主要体现抑制作用的现象，并且抑制作用随SO₂浓度的增大而增加；CO₂由于能在活性炭表面极化，且能与氨基官能团反应生成有利于吸附汞的羰基，促进了活性炭的脱汞性能。

Gaseous Hg0 removal by NH4Cl modified activated carbon

A raw activated carbon and NH₄Cl modified activated carbon were prepared and characterized. Gas-phase Hg⁰ removal performance of the sorbent samples were evaluated in a fixed-bed reactor under N₂ atmosphere. Effect of sorbent size, NH₄Cl solution concentration, SO₂, and CO₂ on mercury removal was explored. The results showed that the porous structure of raw activated carbon does not change during NH₄Cl modification process, but some Cl-containing group remains on activated carbon surface. With the increase of sorbent size, the external mass transfer coefficient and the internal diffusion rate decreases, which indicate that smaller particle size is beneficial to improve mercury removal performance of activated carbon. Due to the generated Cl-containing functional groups can oxidize gaseous Hg⁰ effectively, the oxidation adsorption capability of NH₄Cl-impregnated activated carbon is enhanced. SO₂ in flue gas promotes mercury removal of raw activated carbon, but for NH₄Cl modified activated carbon, SO₂ first promotes mercury removal then inhibits. The inhibition on mercury removal by SO₂ was increased with the concentration of SO₂. Due to the polarization on the surface of activated carbon and the reaction with amino functional groups to form carbonyl groups, CO₂ in flue gas improves mercury removal capability of activated carbon.