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. © 2015, China Coal Society. All right reserved.