Efforts to discern the role of an activated carbon's surface
functional groups on the
adsorption of
elemental mercury (Hg0) and
mercuric chloride demonstrated that chlorine (Cl)
impregnation of a virgin
activated carbon using dilute
solutions of
hydrogen chloride leads to increases (by a factor of 2-3) in fixed-bed capture of these mercury species. A commercially available
activated carbon (DARCO
FGD, NORITAmericas Inc. [
FGD])was Cl-impregnated (Cl-FGD) [5 lb (2.3 kg) per batch] and tested for entrained-flow, short-time-scale capture of Hg0. In an entrained
flow reactor, the Cl-FGD was introduced in Hg0-laden flue
gases (86 ppb of Hg0) of varied compositions with
gas/
solid contact times of about 3-4 s, resulting in significant Hg0 removal (80-90%), compared to virgin
FGD (10-15%). These levels of Hg0 removal were observed across a wide range of very low carbon-to-mercury weight ratios (1000-5000). Variation of the natural
gas combustion flue
gas composition, by doping with
nitrogen oxides and
sulfur dioxide, and the
flow reactor temperature (100-200 degrees C) had minimal effects on Hg0 removal bythe Cl-FGD in these carbon-to-mercury weight ratios. These results demonstrate significant enhancement of
activated carbon reactivity with minimal treatment and are applicable to combustion facilities equipped with downstream
particulate matter removal such as an electrostatic precipitator.
