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THE EFFECT OF WATER (VAPOR-PHASE) AND CARBON ON ELEMENTAL MERCURY REMOVAL IN A FLOW REACTOR
Serre**, S D., B K. Gullett*, AND Y H. Li*. THE EFFECT OF WATER (VAPOR-PHASE) AND CARBON ON ELEMENTAL MERCURY REMOVAL IN A FLOW REACTOR. Presented at AWMA Annual Meeting, Orlando, Florida, 6/24/-28/01.
The paper gives results of studying the effect of vapor-phase moisture on elemental mercury (Hgo) removal by activated carbon (AC) in a flow reactor. tests involved injecting AC into both a dry and a 4% moisture nitrogen (N2) /Hgo gas stream. A bituminous-coal-based AC (Calgon WPL was injected into an Hgo-laden gas stream (124 ppbv) at 150 C at carbon-to-mercury ratios (C:Hg) between 1300 and 4400:1. Adding 4% (vol.) water (H2O) into the gas resulted in about a 10% drop in removal (21-80%), compared to tests in dry N2 (26-89%). The H2O molecules probably form hydrogen bonds with the AC, reducing the number of active sites available for Hgo, The effect of AC moisture content on Hgo removal was also studied. Darco FGD (lignite-based) AC was injected at 100 C and 86 ppbv Hgo. At a C:Hg of 11000:1, Hgo removal for as-received DARCO FGD AC (3% moisture) was 30%. Increasing the moisture content of the AC to 16% resulted in an Hgo removal of 60%. Similar tests, in which th4 surface moisture of the AC was reduced to 0%, resulted in an Hgo removal of <5%. Similar results were obtained with WPL> The effect of AC moisture content on Hgo removal was also tested in a simulated flue ga (small positive impact with FGD; no impact with WPL). Injecting dry AC into a wet (4% moisture) N2 stream did not increase Hgo capture. The moisture probably had insufficient time to diffuse into the AC and modify the carbon-oxygen functional groups that may be responsible for adsorption.