Measurements of homogeneous mercury oxidations by various gas components for simulated exhaust in a flow reactor

Mercury (Hg) emissions have been identified by the EPA as a serious air pollutant. Homogeneous (gas phase) Hg oxidation has been studied in a laminar flow reactor (LFR) using simulated flue gases consisting of mixtures of HCl, NO and O2 in balance N2 gases. The effects of HCl, HCl + O2, HCl + NO, HCl + NO + O2, and temperatures (ambient to 1200C) on emission of elemental Hg were investigated. Elemental Hg decreased with an increase of the HCl concentration and the reaction temperature indicating mercury oxidation. Alone, HCl was found to be a very effective oxidizer for Hg at concentrations of HCl above 90 ppm at 700C or when the reaction temperature was higher than 900C at 50 ppm HCl. For the HCl + O2 and HCl + NO cases, Hg oxidation increased with O2 or NO and with an increase of O2 (from 1 to 5%) while no increase was observed with an increase of NO (from 50 to 300 ppm). This result may be due to the fact that O2 is more likely to produce OH radicals than NO for the HCl + O2 and HCl + NO cases. Mercury oxidation in the HCl + NO + O2 case took place at 600C which is higher than the reaction temperature of 400C in the HCl + O2 case but lower than the reaction temperature of 800C in the HCl + NO case. The results indicated that the presence of NO promoted Hg oxidation for the HCl + NO case, while the NO inhibited Hg oxidation for the HCl + NO + O2 case. Also, the results show that O2 promotes Hg oxidation for the HCl + NO + O2 case.

Measurements of homogeneous mercury oxidations by various gas components for simulated exhaust in a flow reactor Conference Paper