Carbon-enriched coal fly ash as a precursor of activated carbons for SO2 removal

Carbon-enriched coal fly ash was evaluated in this work as a low-cost adsorbent for SO₂ removal from stack gases. The unburned carbon in coal fly ash was concentrated by mechanical sieving and vegetal oil agglomeration. The carbon concentrates were activated with steam at 900 °C in order to develop porosity onto the samples. The performance of these samples in the SO₂ abatement was tested in the following conditions: 100 °C, 1000 ppmv SO₂, 5% O₂, 6% water vapor. A good SO₂ removal capacity was shown by some of the studied samples that can be related to their textural properties. Cycles of SO₂ adsorption/regeneration were carried out in order to evaluate the possibility of thermal regeneration and re-use of these carbons. Regeneration of the exhausted carbons was carried out at 400 °C of temperature and a flow of 25 ml/min of Ar. After each cycle, the SO₂ removal capacity of the sample decreases.