LOW-TEMPERATURE CARBON-BASED PROCESS FOR FLUE-GAS CLEANUP

A low-temperature process employing activated carbon-based catalysts a nd operating downstream of the electrostatic precipitator (ESP) is bei ng developed jointly by Research Triangle Institute (RTI) and the Univ ersity of Waterloo Waterloo). The RTI-Waterloo process is capable of r emoving more than 95% SO2 and 75% NO(x) from coal combustion flue gas. The flue gas leaving the ESP is first cooled to approximately 100-deg rees-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 carbon-based catalyst. Th e SO2-free gas is then reheated to approximately 150-degrees-C and NH3 is injected into the gas stream. It is then passed over a fixed bed o f a different promoted activated carbon-based catalyst to reduce the N O(x) to N2 and H2O. The clean flue gas is then vented to the stack. Th e feasibility of the process has been demonstrated in laboratory-scale experiments using simulated flue gas. Catalysts have been identified which gave the required performance for SO2 and NO(x) removal with les s than 25 ppm NH3 slip. Potential for producing greater than 10N H2SO4 by periodically flushing the SO2 removal reactor was also demonstrate d. Cost for the RTI- Waterloo process was competitive with conventiona l selective catalytic reduction (SCR)-flue gas desulfurization (FGD) p rocess and other emerging combined SO2/NO(x) removal processes.