ACI has achieved moderate to high levels of Hg control. The performance of an activated carbon is related to its physical and chemical characteristics. Generally, the physical properties of interest are surface area, pore size distribution, and particle size distribution. The capacity for Hg capture generally increases with increasing surface area and pore volume. The ability of Hg and other sorbates to penetrate into the interior of a particle is related to pore size distribution.
Carbon sorbent capacity is dependent on temperature, the concentration of Hg in the flue gas, the flue gas composition, and other factors. In general, the capacity for adsorbing Hg2+ will be different than that for Hg0.The selection of a carbon for a given application would take into consideration the total concentration of Hg, the relative amounts of Hg° and Hg2+, the flue gas composition, and the method of capture [electrostatic precipitator (ESP), FF, or dry FGD scrubber
ACI may be used either in conjunction with existing control technologies and/or with additional control such as the addition of an FF. To date ACI has only been evaluated during short-term tests on commercially operating electrical generating plants. Longer-term tests of ACI have been limited to continuous operation, 24 hr/day-7days/week, for a period of less than two weeks at four field test sites. Also, combustion modification, such as coal reburning technology, may increase the carbon in fly ash and yield enhanced Hg capture in PM control devices