Coal fly ash based carbons for SO2 removal from flue gases

Two different coal fly ashes coming from the burning of two coals of different rank have been used as a precursor for the preparation of steam activated carbons. The performance of these activated carbons in the SO2 removal was evaluated at flue gas conditions (100 degrees C, 1000 ppmv SO2, 5% O-2, 6% H2O). Different techniques were used to determine the physical and chemical characteristics of the samples in order to explain the differences found in their behaviour. A superior SO2 removal capacity was shown by the activated carbon obtained using the fly ash coming from a subbituminous-lignite blend. Experimental results indicated that the presence of higher amount of certain metallic oxides (Ca, Fe) in the carbon-rich fraction of this fly ash probably has promoted a deeper gasification in the activation with steam. A more suitable surface chemistry and textural properties have been obtained in this case which explains the higher efficiency shown by this sample in the SO2 removal. (C) 2010 Elsevier Ltd. All rights reserved.