Novel carbon-based process for flue-gas cleanup. Final report.

摘要

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% SO(sub 2) and 75% NO(sub x )from coal combustion flue gas. In the process, the flue gas leaving the ESP is first cooled to approximately 100(degree)C. The SO(sub 2) is then catalytically oxidized to SO(sub 3) which is removed as medium-strength sulfuric acid in a series of periodically flushed trickle-bed reactors containing an activated carbon-based catalyst. The SO(sub 2)-free gas is then reheated to approximately 150(degree)C and NH(sub 3) is injected into the gas stream. It is then passed over a fixed bed of another activated carbon-based catalyst to reduce the NO(sub x) to N(sub 2) and H(sub 2)O. 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 SO(sub 2) and NO(sub x) removal with <25 ppM NH(sub 3) slip. Potential for producing up to 10 N sulfuric acid by periodically flushing the SO(sub 2) 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 SO(sub 2)/NO(sub x) removal processes.