389647 Elemental Mercury Oxidation in an Electrostatic Precipitator with in-Situ Soft X-Rays

Thursday, November 20, 2014: 9:50 AM
M101 (Marriott Marquis Atlanta)
He Jing, Xiaofei Wang, Wei-Ning Wang and Pratim Biswas, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Saint Louis, MO

Nonthermal plasma--based techniques are considered promising for oxidizing elemental mercury (Hg0) in flue gas from coal combustion. In this study, we investigated Hg0 oxidation in a DC (direct current) corona electrostatic precipitator (ESP) coupled with in-situ soft X-rays. Soft X-rays enhanced Hg0 oxidation by promoting electron generation, creating a large quantity of oxidizing radicals, such as monoatomic oxygen (O) and ozone molecules (O3). Positive corona discharges worked better in Hg0 oxidation than negative ones, because they generate more high energy electrons, a finding which was supported by plasma simulations of soft X-ray--coupled ESP. Reaction mechanisms were further studied in single gas environments where pure oxygen (O2), nitrogen (N2), or carbon dioxide (CO2) was the carrier gas. In the CO2 case, Hg0 could not be oxidized by ESP operation alone, but it could be oxidized with ESP and soft X-rays. This result indicates that soft X-ray enhancement has even greater potential for Hg0 oxidation by ESP when high concentrations of CO2 are present in flue gas, such as in the oxy-combustion case. The effects of titanium dioxide (TiO2), silicon dioxide (SiO2), and potassium iodide (KI) particles on the oxidation processes were also studied. When the soft X-ray--coupled ESP technology is applied to mercury capture from flue gas, it still retains the co-benefit of capturing particles.

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