Carbon dioxide sequestration by accelerated carbonation of cement kiln dust (CKD)

Wastes from cement industry are gaining interest as source material for carbon dioxide sequestration through mineral carbonation. This paper reports the preliminary results of a study where aqueous routes accelerated carbonation (both wet and slurry-phase) was applied to Cement Kiln Dust with the aim of assessing the extent of CO2 sequestration and the reaction kinetics under varying operating conditions. The effect of parameters such as liquid-to-solid (L/S) ratio, CO2 pressure, temperature and process duration was evaluated. CKD was highly reactive towards CO2, allowing for a CO2 sequestration capacity up to 9.8% and a Ca-to-carbonate conversion yield up to 74%. Higher uptakes and carbonation yields were attained in slurry-phase carbonation test if compared to wet-route treatments. At the more energy-intensive operating conditions applied, CO2 sequestration did not generally improve, suggesting that a cost-effective process under mild condition could be tested and optimized.