Experimental and Kinetic Analysis of H2O on Hg0Removal by Sorbent Traps in Oxy-combustion Atmosphere

Oxy-combustion technology is under development for CO2capture. H2O could influence the Hg0removal by sorbent traps in an oxy-combustion atmosphere. A study of the effects of H2O on Hg0removal by biomass char under oxy-combustion conditions is presented in this paper. The kinetic model analysis was conducted to study the adsorption process of Hg0, which included a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and intraparticle diffusion kinetic model. Experimental results showed that a low-level of H2O had a promoting effect on the adsorption of Hg0, and high-level of H2O had an inhibiting effect. A high concentration of H2O would form a water film on the surface of sorbent traps to hinder the removal of external mass transfer on Hg0. Although the adsorption rate of Hg0depended both on external mass transfer and intraparticle diffusion, external mass transfer was a more important controlling factor. It was found that physical adsorption was one of the main forms of Hg0removal on the surface of sorbent traps, owing to the large specific surface area and good pore structure of the modified corn straw char. The removal of Hg0was mainly attributed to capture by physical adsorption and the formation of HgO by chemisorption.