Industrial grade calcium sulfide modified by selenium for elemental mercury removal from flue gas

Metallic sulfides (MS) adsorption is considered as an effective method to remove Hg-0 from coal-fire flue gas. Se modification can significantly improve Hg-0 removal process on MS due to the high affinity constant between Se and Hg-0. CaS as a production from wet flue gas desulfurization has potential Hg-0 removal ability. Therefore, in the present work, Se modified industrial grade CaS was prepared to remove Hg-0 and the effect of the ratio of CaS to Se on Hg0 removal process was studied. Characterization results show that Ca-1-Se-1.7 had the richest porous structure and largest surface area resulting in more available surface active sites. In addition, Ca-1-Se-1.7 has the highest content of Se-, who can remove Hg-0 via Hg-0(ad) + Se-2(2-) -> HgSe + Se2- As a result, Ca-1-Se-1.7 has the highest Hg-0 removal efficiency of nearly 100 % from 60 degrees C to 100 degrees C, and it reaches 85 % even in the presence of 500 ppm SO2. The Hg-0 adsorption kinetic was well defined by the pseudo-first-order kinetic model and internal diffusion model, so that Hg-0 diffusion especially internal diffusion is the primary controlling step.