Activated coke impregnated with cerium chloride used for elemental mercury removal from simulated flue gas

摘要

Gas-phase elemental mercury (Hg~0) removal by activated coke impregnated with cerium chloride (A1CC) was studied under simulated flue gas conditions. Brunauer-Emmett-Teller (BET), X-ray diffractogram (XRD), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX) and X-ray photoelectroh spectroscopy (XPS) analyses were used to characterize the samples. The effects of CeCl3 loading values, reaction temperatures and individual flue gas components including O2, NO, SO2 and H2O (g) on Hg~0 removal efficiency of AICC samples were investigated. Results showed that Hg~0 removal efficiency of AC was significantly enhanced by CeCl3. The optimal CeCl3 loading value and reaction temperature was around 6% and 170°C, respectively. Additionally, the experiment results of effects of flue gas components on Hg~0 removal efficiencies showed that when O2 was present in the flue gas, NO and SO2 were observed to promote Hg~0 oxidation. However, in the absence of O2, SO2 showed an insignificant inhibition on Hg~0 removal. Furthermore, when H2O was added into the flue gas, the Hg~0 removal capacity had a slight declination. The analyses of XRD and XPS showed that Ce_xO_y and C-Cl were generated on the surface of AICC and those active elements had remarkably positive effects on the Hg~0 removal. The reaction mechanism indicated that Hg~0 oxidation was achieved through two pathways: one was that Hg~0 bond with CeO2 and was converted by the catalytic oxidation of valence variable cerium; the other was that Hg~0 reacted with C-Cl on the sample and was oxidized favored by chloride presence. And according to Hg 4f XPS analysis, the mercury on the surface of AICC was mainly in the form of mercuric oxide (HgO) and mercuric chloride (HgCl2).