Coal fly ash based carbons for SO_2 removal from flue gases

摘要

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 SO_2 removal was evaluated at flue gas conditions (100 ℃. 1000 ppmv SO_2, 5% O_2, 6% H_2O). 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 SO_2 removal capacity was shown by the activated carbon obtained using the fly ash coming from a subbiturninous-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 SO_2 removal.