The measurement and control of mercury emissions from utility power plants continue to be the subjects of much study. In a program funded by the Department of Energy, Physical Sciences Inc. (PSI) is developing a mercury sorbent using a zeolite material with a proprietary agent for improved capture of elemental as well as oxidized mercury.

Previous research at PSI has shown the feasibility of using zeolites for mercury capture. Results of this work showed that a treated zeolite sorbent performed as well as a treated activated carbon in removing total mercury from the flue gas, and that treating the zeolite improved elemental mercury capture compared to the untreated zeolite.

In the current work two types of treated zeolite sorbent and one type of activated carbon were injected into flue gases from combustion of a Pittsburgh seam bituminous coal with the purpose of evaluating sorbent efficiency under conditions that approximate full-scale utilities with electro-static precipitators. The gas temperatures and residence times were similar to those found in power plant flue gas ducts and were in the range of 130 to 200°C and 2 s, respectively. The mercury concentration varied in the range of 30 to 60 µg/m³. As in the previous fixed bed work, mercury concentration and speciation were measured using the modified Ontario Hydro Method. The mercury removal efficiencies in the experiments were zeolite sorbent was used varied in the range of 45 to 92% for sorbent to Hg ratios in the range of 5,000 to 96,000. When no sorbent was injected, ash did remove some mercury, but in the presence of sorbent the role of ash in mercury removal appeared to diminish, presumably due to the higher reactivity of the sorbent with respect to the ash.