Enhancement in cyclic stability of the CO2 adsorption capacity of CaO-based sorbents by hydration for the calcium looping cycle

In this paper, the reactivation of limestone was effectively enhanced and recovered by steam and/or liquid water hydration processes. The decay rate of the activity in carbonation conversion was improved by the steam hydration of the sorbents during decarbonation/carbonation reactions. The carbonation conversion activity of limestone with a particle size of 1.5 mu m remains at 65% with hydration under 2.9 mol% steam after 20 decarbonation/carbonation cycles, while the un-hydrated sorbent shows a lower carbonation conversion of 34%. The activity preservation in the carbonation conversions of three representative particle size ranges of 1.5, 37-74, and 250-500 mu m are 30, 14, and 6% after 20 cycles, respectively, with a hydration treatment of 2.9 mol% steam. Pore formation and roughness on the sorbents induced by steam hydration contributed significantly to the enhanced carbonation conversion during the decarbonation/carbonation cycles. The sorbent, with a particle size of approximately 1.5 mu m, exhibited higher regeneration and recovery of carbonation conversion. Combined with the liquid water hydration, the carbonation conversion activity of the limestone can recover 80-90% of the original. (C) 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.