KBr和KI改性黏土脱除模拟烟气中的单质汞

黏土是一种非常廉价的天然矿物，为了考察溴和碘改性黏土（膨润土）脱除烟气中单质汞的特性，采用浸渍法分别制备了KBr和KI改性黏土（KBr-clay和KI-clay）。在固定床吸附实验台上进行了脱除Hg⁰的实验研究，考察不同的负载量、吸附温度以及烟气中SO₂和水蒸气等对KI-clay和KBr-clay脱除单质汞的影响。研究结果表明：改性后黏土的比表面积、孔隙结构未发生显著的改变，表面官能团也没有发生本质的变化。KI-clay和KBr-clay脱汞能力大大提高，在同等实验条件下，KI-clay脱汞性能优于KBr-clay。研究表明单质汞在改性黏土表面产生了化学吸附，烟气中低浓度SO₂的存在对汞脱除有一定的促进作用，在相同的实验条件下，SO₂ 对KBr-clay促进作用更加明显，但水蒸气在低温下对脱汞具有很强的抑制作用，提高吸附温度可以消弱水蒸气的负面影响。

Removal of element mercury from simulated flue gas by clay modified with KBr and KI

Clay is a kind of cheap natural minerals in China. In order to study their performance for removal of elemental mercury in flue gas, the clays were modified by impregnating KBr and KI to prepare KBr-clay and KI-clay. A series of bench adsorption tests was carried out in a fixed bed to examine the removal efficiency of elemental mercury from simulated flue gas by KBr-clay and KI-clay. The effect of halogen loadings, adsorbent temperatures and the flue gas components (SO₂ and H₂O) on the performance was studied. The result showed that the modification did not much change the specific surface area and the pore structure of the clays, while there was little variation also in the surface functional groups. The sorption capacity of elemental mercury by KBr-clay and KI-clay was drastically improved, and it is of better activity for KI-clay than for KBr-clay under the same experimental conditions. The chemical adsorption played a dominant pole in the process of the elemental mercury removal. SO₂ was found to have a promotional effect on elemental mercury adsorption, and the promotional effect of SO₂ was more apparent for KBr-clay. H₂O vapor exhibited a inhibitory effect on elemental mercury adsorption, but the effect decreased with the raising reaction temperature.