Investigation on synergistic oxidation behavior of NO and Hg~0 during the newly designed fast SCR process

摘要

In the present study, elemental mercury (Hg-0) oxidation behavior in the NO oxidation step of fast SCR process was investigated. The Mn doped CeO2-ZrO2 (CZM0.3) was selected as the catalyst, due to its superior oxygen storage capacity. The results showed that NO could be oxidized efficiently over the catalyst at around 250 degrees C under the atmosphere of NO/O-2/N-2. In the Hg-0/NO/O-2/N-2 reaction system, NO oxidation reaction remarkably improved Hg-0 oxidation efficiency. Two domination reaction pathways were proposed to interpret the influence of NO oxidation reaction on Hg-0 oxidation: one through a heterogeneous oxidation process, and the other through a homogeneous reaction. In the heterogeneous oxidation process, NO was adsorbed on the active sites and activated by the surface oxygen to form more active intermediates for Hg-0 oxidation. Hg-0 was probably oxidized in its gaseous state, since the affinity between NO and the catalyst was stronger than that between Hg-0 and the catalyst. The other reaction pathway was a homogeneous route, during which the gaseous NO2 generated by NO oxidation could oxidize the gaseous Hg within the designed reaction conditions. According to the present research, synergistic oxidation of NO and Hg-0 in the first step of fast SCR appears to be a promising way to remove Hg-0 and NOx in coal-fired power plants.