UPTAKE OF NOX BY ACTIVATED CARBONS - BENCH-SCALE AND PILOT-PLANT TESTING

The possibility of selectively removing NOx from gas containing CO2, N -2, O-2, H2O, SO2 and NOx has been examined using bench-scale and pilo t-scale experimentation. These results have shown that NO can be selec tively sequestered from the gas if the oxygen concentration is high en ough and the SO2 concentration is low enough. Oxygen enhances the amou nt of NO removed, and promotes the conversion of NO to NO2 (via NO+1/2 O(2)-->NO2) and the adsorption of NO2 within the carbons' micropores. The carbon is not consumed if during NO2 desorption its temperature is maintained below about 200 degrees C. The presence of SO2 inhibits th e oxidation of NO and the subsequent storage of NO2 within micropores but, at concentrations typical to gases after post-combustion sulfur s crubbers, such inhibition is an immediate effect probably associated w ith selective site poisoning rather than a cumulative effect associate d with pore blocking or sulfur retention. The possibility of removing NO and NO2 from combustion flue gas and the extent to which fines were produced during pilot-plant testing of activated carbons will also be discussed. Wear patterns on the carbon surface subsequent to the pilo t-plant studies and NOx uptake calculated from gas-phase and sorbent a nalyses are compared to data from the bench-scale experimentation. Inf ormation needed for more complete understanding of the interaction of NO+SO2 on and within carbon is discussed. (C) 1997 Elsevier Science Lt d.