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THE ADVANTAGE OF ILLINOIS COAL FOR FGD REMOVAL OF MERCURY
Citation:
Ghorishi, S. B., W. Jozewicz, AND B K. Gullett*. THE ADVANTAGE OF ILLINOIS COAL FOR FGD REMOVAL OF MERCURY. Presented at Incineration and Thermal Treatment Technology Conf, New Orleans, 5/13-17/02.
Description:
The paper gives results of an investigation conducted to characterize and modify mercury (Hg) speciation in Illinois coal combustion flue gas so that a Hg control strategy can be implemented in conventional flue gas desulfurization (FGD) units. Hg, in trace concentration in coal, is readily volatilized during coal combustion and leaves the high-temperature zone as gas-phase elemental Hg [Hg(0)]. Previous results have shown that, as the flue gas is cooled, a portion of the Hg(0) is converted, primarily to mercuric chloride (HgCl2), in the presence of catalytically active surfaces such as certain fly ashes. Unlike Hg(0), HgCl2 is highly soluble in water and has a high affinity for alkaline sorbents; it can, therefore, be easily removed in wet scrubbers and spray dryers (FGD units). This two-task study examined the effect of injecting Illinois coal combustion residues (.ICCRs) on the conversion of Hg(0) to HgCl2 in coal combustion flue gases. Task I studied Hg(0) oxidation using a fixed-bed, bench- scale reactor in a simulated Illinois coal combustion environment. Various types of ICCRs were examined to determine active residues in the oxidation of Hg(0). The most active ICCR (a bottom ash sample) was chosen for Task II, which consisted of two subtasks. In subtask I, the active bottom ash sample was injected in a pilot-scale combustor while burning natural gas appropriately doped. In subtask II, a representative Illinois coal was combusted in the pilot-scale combustor. As with most bituminous coals, the combustion flu gas of this coal was dominated by oxidized forms of Hg (most probably HgCl2).