ZnCl_2溶液对褐煤半焦表面性质及其中高温脱汞性能的影响

Influence of ZnCl_2 solution impregnation on the surface properties of lignite semi-coke and its mercury removal performance at elevated temperature

利用ZnCl_2溶液对褐煤进行浸渍后在700℃条件下热解制备改性半焦,采用N2吸附/脱附、傅里叶变换红外光谱、X射线光电子能谱等手段对ZnCl_2处理前后两种半焦表面物化性质进行了表征,在小型固定床反应器上研究了ZnCl_2溶液浸渍处理前后褐煤半焦对气态单质汞(Hg^0)的脱除性能.结果表明,经过ZnCl_2处理得到的半焦(ZSC)具有发达的孔隙结构,其表面含氧官能团含量和数量有所提高,并出现了新的C-Cl基团;在100~360℃温度范围内,制备的改性半焦ZSC的脱汞效率随温度升高而降低,但在中高温条件下仍表现出良好的脱汞性能;在化学吸附过程中,气态Hg0被C-Cl基团氧化为HgCl或HgCl_2,同时Hg^0与半焦表面含氧官能团结合生成HgO,Hg^0最终以HgCl_2或HgO的形式附着在半焦表面.

The modified semi-coke（ZSC） was obtained by the pyrolysis of ZnCl2-impregnated lignite at 700℃. N2adsorption/desorption, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the surface physical and chemical properties of original and modified semi-coke, and the gaseous elemental mercury（Hg0） removal performance of two kinds of semi-coke has been investigated in a lab-scale fixed-bed reactor. The experimental results showed that ZSC had more developed hole structure, large specific surface area and abundant C—Cl groups. The mercury removal efficiency of ZSC decreased as the adsorption temperature was raised in the temperature range of 100℃ to 360℃. Generally, the ZSC exhibited good mercury removal performance at elevated temperatures. During the chemisorption process, the Hg0 was partly oxidized to Hg Cl or Hg Cl2 by C—Cl groups, and the others reacted with oxygen contained functional groups on the surface of semi-coke to generate Hg O simultaneously. Finally, the Hg0 was captured in the form of Hg Cl2 or Hg O on the surface of semi-coke.