Study on removal of elemental mercury from simulated flue gas over activated coke treated by acid

摘要

This work addressed the investigation of activated coke (AC) treated by acids. Effects of AC samples, modified by ether different acids (H2SO4, HNO3 and HClO4) or HClO4 of varied concentrations, on Hg-0 removal were studied under simulated flue gas conditions. In addition, effects of reaction temperature and individual flue gas components including O-2, NO, SO2 and H2O were discussed. In the experiments, Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were applied to explore the surface properties of sorbents and possible mechanism of Hg-0 oxidation. Results showed that AC sample treated by HClO4 of 4.5 mol/L exhibited maximum promotion of efficiency on Hg-0 removal at 160 degrees C. NO was proved to be positive in the removal of Hg-0. And SO2 displayed varied impact in capturing Hg-0 due to the integrated reactions between SO2 and modified AC. The addition of O-2 could improve the advancement further to some extent. Besides, the Hg-0 removal capacity had a slight declination when H2O was added in gas flow. Based on the analysis of XPS and FTIR, the selected sample absorbed Hg-0 mostly in chemical way. The reaction mechanism, deduced from results of characterization and performance of AC samples, indicated that Hg-0 could firstly be absorbed on sorbent and then react with oxygen-containing (C-O) or chlorine-containing groups (C-Cl) on the surface of sorbent. And the products were mainly in forms of mercuric chloride (HgCl2) and mercuric oxide (Hg-0). (C) 2014 Elsevier B.V. All rights reserved.