Simultaneous removal of Hg0 and NO from simulated flue gas over columnar activated coke granules loaded with La2O3-CeO2 at low temperature

Abstract

A series of industrial desulfuration activated cokes loaded La2O3 and CeO2 (LaCe/AC) were employed for simultaneous NO and Hg0 removal from simulated flue gas. The physicochemical characteristics of samples were characterized by BET, XRD, SEM, NH3-TPD, TGA and XPS. 25%LaCe/AC exhibited outstanding NO removal efficiency (91.3%) and superior Hg0 removal efficiency (94.3%) at 180 °C. The effects of Hg0 on SCR reaction and SCR atmosphere on Hg0 oxidation were investigated. The results demonstrated that Hg0 had negligible impact on NO removal efficiency while NO evidently promoted Hg0 removal efficiency. Meanwhile, NH3 had an adverse effect on Hg0 removal efficiency. The slightly inhibitive effect derived from the existence of H2O or SO2 was also detected. The NO removal mainly followed the Langmuir-Hinshlwood mechanism while the Hg0 removal mechanism was attributed to the combination of physisorption and chemisorption and catalytic oxidation. Especially, the relative contributions of physisorption and chemisorption and catalytic oxidation were distinguished and calculated by designed mercury conversion and desorption tests, the results indicated chemisorption displayed the predominant role. In addition, the stability test of 27 h was carried out and eventually the sample maintained 84.5% Hg0 removal efficiency and 89.5% NO removal efficiency, indicating its potentially large-scale industrial application at low temperatures in the foreseeable future.