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A low-temperature process employing activated carbon-based catalysts and operating downstream of the electrostatic precipitator (ESP) was evaluated jointly by Research Triangle Institute (RTI) and the University of Waterloo (Waterloo). The RTI-Waterloo process was projected to be capable of removing more than 95% SO2 and 75% NOxfrom coal combustion flue gas. In the process, the flue gas leaving the ESP is first cooled to approximately 100°C.The SO2 is then catalytically oxidized to SO3 which is removed as medium-strength sulfuric acid in a series of periodically flushed trickle-bed reactors containing an activated carbonbased catalyst. The SO2-free gas is then reheated to approximately 150°C and NH3 is injected into the gas stream. It is then passed over a fixed bed of another activated carbonbased catalyst to reduce the NOxto N2 and H20. The clean flue gas is then vented to the stack. The feasibility of the process has been demonstrated in laboratory-scale experiments using simulated flue gas. Catalysts have been identified that gave the required performance for SO2 and NOx removal with <25 ppm NH 3 slip. Potential for producing up to 10 N sulfuric acid by periodically flushing the SO2 removal reactor and further concentration to industrial strength 93.17% sulfuric acid was also demonstrated. Using the results of the experimental work, an engineering evaluation was conducted. Cost for the RTI-Waterloo process was competitive with conventional selective catalytic reduction (SCR) -flue gas desulfurization (FGD) process and other emerging combined SO2/NO x removal processes. i i iii ACKNOWLEDGMENT This study was sponsored by the U.S. Department of Energy (DOE) under contract No. DE-AC22-91PC91345. The authors would like to acknowledge with gratitude the guidance provided by the DOE Contracting Officer's Representative, Ms. Diane Revay Madden, of the Pittsburgh Energy Technology Center (PETC). Helpful discussions were also held with other PETC personnel, particularly Charlie Drummond and Chuck Schmidt. Calgon Carbon, Degussa Corporation, and DMT (Germany) provided a number of carbon samples for testing free of charge. David Biscan of Calgon Carbon arranged a presentation of the RTI-Waterloo process to Calgon personnel in Pittsburgh.

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