Development of a Cl-Impregnated Activated Carbon for Entrained-Flow Capture of Elemental Mercury

Abstract

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.

The role of unburned carbon concentrates from fly ashes in the oxidation and retention of mercury

“…This could be due to HCl binding onto the surface of the fly ash as it does onto activated carbons [29], favouring Hg retention. To confirm this hypothesis the ashes with the lowest and highest Hg retention capacities, CTE-O and CTL-EC, were first treated with HCl gas at 0.5 L min -1 during 15 hours and then, the samples were used as .…”

Surface Compositions of Carbon Sorbents Exposed to Simulated Low-Rank Coal Flue Gases

“…9,14 However, Cl-and sulfur-bearing surface functional groups that form via addition of acid gases to the basic sorbent groups during exposure of carbons to flue gas are not well characterized.…”

Comparison of Mercury Emissions in USA and China-The Way of Effective Control of Hg from the Power Plant

“…Typically, activated carbon injection is used to capture oxidized mercury [21][22][23][24][25][26][27][28][29][30][31][32]. A major limitation with using activated carbon is that in flue gases with low halogen concentrations a large amount of activated carbon needs to be added to the system to effectively control Hg0.…”