SOx and NOx absorption based removal into acidic conditions for the flue gas treatment in oxy-fuel combustion

In order to reduce simultaneously nitrogen and sulfur oxides contained in oxyfuel exhaust gases (composed mostly of carbon dioxide), an original absorption technique is proposed consisting in the scrubbing with aqueous acidic solutions containing hydrogen peroxide to oxidize NOx and SO2 in HNO3 and H2SO4, forming a mixture which can be reused or separated. Individual and combined effects of acids and H2O2 concentrations in the liquid phase were here observed on the NOx and SOx absorption efficiencies. Absorption tests were achieved at 20 degrees C and atmospheric pressure in a cables-bundle contactor; a range of partial pressures (600-2000 ppm SO2, 5000 ppm NOx) and liquid phase concentrations (0-4 mol/l for each acid, 0-1 mol/l for H2O2) was investigated. While the presence of acids, especially H2SO4, has a negative effect on SO2 absorption rates, more acid conditions were found to promote the global NOx absorption. Comparatively to the use of classical alkaline conditions leading to slightly higher SOx and NOx absorption efficiencies, acid solutions allow to avoid the undesired absorption of CO2 and the extra-consumption of the reactant. (C) 2011 Published by Elsevier Ltd.