CaO is being proposed as a regenerable sorbent of CO2 via a carbonation/calcination loop. It is well known that natural sorbents lose their capacity to capture CO2 with the number of cycles due to textural degradation. In coal combustion systems, reaction with the SO2 present in flue gases also causes sorbent deactivation. This work investigates the effect of partial sorbent sulfation on the amount of CaO used in systems where both carbonation and sulfation reactions are competing. We have found that SO2 reacts with the deactivated CaO resulting from repetitive calcination/carbonation reactions. Therefore, the deactivation of CaO as a result of the presence of SO2 is lower than one would expect if one assumes that SO2 reacts only with active CaO. This work shows that changes in the texture of the sorbent due to repetitive carbonation/calcination cycles tend to increase the sulfation capacity of the sorbents tested. This suggests that the purge of deactivated CaO obtained from a CO2 capture loop could be a more effective sorbent of SO2 than fresh CaO.

This work is partially funded by the European Commission (C3-Capture) and the Spanish Ministry of Education ("Juan de la Cierva" program).

6 pages, 10 figures.-- Printed version published Mar 5, 2008.

Peer reviewed