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SPECIATION OF MERCURY IN THE PRESENCE OF COAL AND WASTE COMBUSTION FLY ASHES
Citation:
Lee*, C W., J D. Kilgroe*, AND S. B. Ghorishi. SPECIATION OF MERCURY IN THE PRESENCE OF COAL AND WASTE COMBUSTION FLY ASHES. Presented at AWMA Conference, Salt Lake City, UT, 6/18-22/2000.
Description:
The paper gives results of a study that focused on the oxidation of elemental mercury (Hgo) in the presence of both complex, four-component, model fly ashes, and actual coal combustion fly ashes collected from a pilot plant. Steady-state oxidation of Hgo promoted by the four-component model fly ashes (containing calcium oxide, CaO) was reached at much slower rates, compared to those obtained using the three-component model fly ashes (containing no CaO) of a previous study. ( NOTE: In the previous study, speciation of mercury, or more specifically oxidation of Hgo, was investigated experimentally in simulated flue gases, and in the presence of three-component model fly ashes). The partial removal of gas-phase hydrogen chloride (HC1 by CaO in the CaO-containing model fly ashes may have reduced the available chlorinating agent, resulting in slower oxidation of Hgo. All the coal fly ashes were more active in the oxidation of Hgo in the presence of nitrogen oxides (NOx), compared to HC1. These results agree with those of the previous model fly ash studies, and those from other researchers. The product of heterogeneous reaction of Hgo with NOx has been identified by other researchers as mercury nitrate monohydrate, which is rather volatile and stable under flue gas cleaning conditions. Sodium oxide and nickel may also be active in oxidizing Hgo.