Investigation on synergistic oxidation behavior of NO and Hg0 during the newly designed fast SCR process

Abstract In the present study, elemental mercury (Hg 0 ) oxidation behavior in the NO oxidation step of fast SCR process was investigated. The Mn doped CeO 2 -ZrO 2 (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 °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 NO 2 generated by NO oxidation could oxidize the gaseous Hg 0 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 NO x in coal-fired power plants.