煤焦改性对烟气中不同形态汞的吸附性能

为探究煤焦吸附剂对烟气中单质汞和氯化汞的吸附特性，选取小龙潭褐煤和大同烟煤在管式炉氮气氛围下热解制焦，采用美国Micromeritics公司ASAP2020自动吸附仪测定煤焦比表面积和孔径特性。测试结果表明，低阶煤小龙潭褐煤拥有更大的比表面；制焦过程中的升温速率以及停留时间也会影响煤焦的比表面积。煤焦比表面积主要受挥发分的析出和颗粒的受热变形影响。在实验室固定床台架分别对煤焦的单质汞和氯化汞的吸附性能进行了实验研究。吸附实验表明,煤焦吸附Hg0和HgCl2性能与煤焦的比表面积成显著的正相关关系；孔容积的增加也能够促进煤焦的吸附性能。经过盐酸和氢氧化钠溶液改性后的煤焦对单质汞和氯化汞吸附能力都有所提高，盐酸改性引入的表面官能团促进了改性煤焦对Hg0的氧化和化学吸附；根据相似相容原理，氢氧化钠溶液改性引入的-OH改善了煤焦对氯化汞的吸附。

Adsorption of different mercury forms from flue gas by modified coal char

In order to study the adsorption performances of the coal char on Hg0 and HgCl2 in the flue gas,coal chars were produced with the Xiaolongtan lignite and Datong bitumite in the tube furnace in nitrogen atmosphere pyrolysis,with different heating rates and varied retention times.The specific surface area was analyzed by Micromeritics ASAP2020 auto-adsorption analyzer to obtain N2 adsorption isotherms,the results suggest that the Xiaolongtan lignite obtains larger surface area.The heating rate and the retention time vary the specific surface area of coal char.It is considered that the volatile matter evolution and the temperature distortion affect the specific surface area.The adsorption performances of mercury removal by these sorbents were conducted in the laboratory scale packed-bed reactor system.The property of the Hg0 and HgCl2 sorption by the raw chars is positively correlated with the specific surface area,and the sorption is physical absorption.The increase of pore volume also promotes the adsorption performance of the coal char.The property of the Hg0 and HgCl2 sorption by the modified sorbents improves markedly,which indicates that the surface functional groups（—Cl，—OH）on the surface of the HCl-modified char promotes the mercury oxidation,which belongs to chemical adsorption.Meanwhile,according to the theory of similarity and intermiscibility,the surface hydroxy groups promotes the sorption of the NaOH-modified char.