Calcium looping is an energy-efficient CO2 capture technology that uses CaO as a regenerable sorbent. One of the advantages of Ca-looping compared with other postcombustion technologies is the possibility of operating with flue gases that have a high SO2 content. However, experimental information on sulfation reaction rates of cycled particles in the conditions typical of a carbonator reactor is scarce. This work aims to define a semiempirical sulfation reaction model at particle level suitable for such reaction conditions. The pore blocking mechanism typically observed during the sulfation reaction of fresh calcined limestones is not observed in the case of highly cycled sorbents (N > 20) and the low values of sulfation conversion characteristic of the sorbent in the Ca-looping system. The random pore model is able to predict reasonably well, the CaO conversion to CaSO4 taking into account the evolution of the pore structure during the calcination/carbonation cycles. The intrinsic reaction parameters derived for chemical and diffusion controlled regimes are in agreement with those found in the literature for sulfation in other systems. (C) 2011 American Institute of Chemical EngineersAIChE J, 2012