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

Abstract

Abstract 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 NO x and SO 2 in HNO 3 and H 2 SO 4 , forming a mixture which can be reused or separated. Individual and combined effects of acids and H 2 O 2 concentrations in the liquid phase were here observed on the NOx and SOx absorption efficiencies. Absorption tests were achieved at 20 °C and atmospheric pressure in a cables-bundle contactor; a range of partial pressures (600-2000 ppm SO 2 , 5000 ppm NO x ) and liquid phase concentrations (0-4 mol/l for each acid, 0-1 mol/l for H 2 O 2 ) was investigated. While the presence of acids, especially H 2 SO 4 , has a negative effect on SO 2 absorption rates, more acid conditions were found to promote the global NO x 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 CO 2 and the extra-consumption of the reactant.