On the relevant influence of limestone crystallinity on CO2

8 We analyze the role of limestone crystallinity on its CO2 capture performance when subjected 9 to carbonation/calcination cycles at conditions mimicking the Ca-looping (CaL) technology 10 for post-combustion CO2 capture. The behavior of raw and pretreated limestones (milled and 11 thermally annealed) is investigated by means of thermogravimetric analysis (TGA) tests under 12 realistic sorbent regeneration conditions, which necessarily involve high CO2 partial pressure in 13 the calciner and quick heating rates. The pretreatments applied lead to contrasting effects on 14 the solid crystal structure and, therefore, on its resistance to solid-state diffusion. Our results 15 show that decarbonation at high CO2 partial pressure is notably promoted by decreasing 16 solid crystallinity. CaO regeneration is fully achieved under high CO2 partial pressure at 17 900◦C in short residence times for the milled limestone whereas complete regeneration for raw 18 limestone requires a minimum calcination temperature of about 950◦C. Such a reduction of the 19 calcination temperature and the mitigation of multicyclic capture capacity decay would serve 20 to enhance the efficiency of the CaL technology. On the other hand, the results of our study 21 suggest that the use of highly crystalline limestones would be detrimental since excessively 22 high calcination temperatures should be required to attain full decarbonation. 23