Reactivity of CaO derived from nano-sized CaCO<inf>3</inf> particles through multiple CO<inf>2</inf> capture-and-release cycles

The carbonation characteristics of pure CaO derived from nano-sized CaCO3 were investigated as part of a multi-cycle performance study which showed potential for exploiting the properties of nano-sized CaO sorbents in a continuous CO2 capture-and-release process. To help understand the approach to the decay asymptote, which is established through multiple capture-and-release cycles, a qualitative model was proposed. The rate of approach and residual conversion defined by the decay asymptote represents the establishment of an equilibrium between the pore volume and surface area loss during thermal sintering; and the pore volume and surface area regeneration as a consequence of a solid-state diffusion mechanism, and the subsequent release of CO2 in the next calcination cycle. This qualitative explanation is valid for all CaO derived CO2 sorbents. © 2008 Elsevier Ltd. All rights reserved