Calcium looping for CO2 capture: sorbent enhancement through doping

Abstract Calcium oxide has been proposed as a regenerable sorbent for separating CO 2 from flue gas at high temperatures. It is well known that natural sorbents (i.e., CaO derived from natural limestone) lose their capture capacity as the number of the carbonation/calcination cycles increases. If the behaviour of the sorbent can be improved (i.e., the decay in reactivity of sorbent reduced or residual reactivity of sorbent increased), the viability of a CaO-based CO 2 capture scheme could be improved. One potential method to achieve this is doping the sorbent with different salts. In this work, a simple wet impregnation method has been used to dope two different limestones using solutions of KCl and K 2 CO 3 with different concentrations. Doped samples were then subjected to repeated carbonation/calcination cycles in both a Fluidized Bed Reactor (FBR) and a Thermogravimetric Analyser (TGA) in order to compare their reactivity in both cases. The results obtained show that samples doped with 0.5 M solution of KCl have a decreased reactivity over the initial cycles, but an increased long-term reactivity in both the FBR and the TGA, with improved results observed in the FBR. Sorbent doping could prove to be a relatively inexpensive method of improving the reactivity of sorbent for the calcium looping cycle for CO 2 capture.