CO2 Capture Capacity of CaO in Long Series of Carbonation/Calcination Cycles

6 pages, 11 figures, 1 table.-- Printed version published Dec 20, 2006.Calcium oxide can be an effective sorbent to separate CO2 at high temperatures. When coupled with a calcination step to produce pure CO2, the carbonation reaction is the basis for several high-temperature CO2 capture systems. The evolution with cycling of the capture capacity of CaO derived from natural limestones is experimentally investigated in this work. Long series of carbonation/calcination cycles (up to 500) varying different variables affecting sorbent capacity have been tested in a thermogravimetric apparatus. Calcination temperatures above T > 950°C and very long calcination times accelerate the decay in sorption capacity, while other variables have a comparatively modest effect on the overall sorbent performance. A residual conversion of about 7−8% that remains constant after many hundreds of cycles and that seems insensitive to process conditions has been found. This residual conversion makes very attractive the carbonation/calcination cycle, by reducing (or even eliminating) sorbent purge rates in the system. A semiempirical equation has been proposed to describe sorbent conversion with the number of cycles based on these new long data series.This work is partially funded by the European Commission (ISCC and C3Capture projects) and the Spanish Ministry of Education ("Juan de la Cierva" contract to G.S.G.).Peer reviewe