The present study addresses steam hydration as a reactivation technique of the CO2 capture ability of spent limestone-based sorbents from fluidized bed calcium looping systems. A reference, high-calcium, reactive limestone was first deactivated by carrying out lab-scale fluidized bed calcium looping tests (calcination at 940°C in a 70% CO2 atmosphere; carbonation at 650°C in a 15% CO2 atmosphere), and then it was steam hydrated (at 250°C in a 50% steam atmosphere) in the same fluidized bed, for times ranging from 10 to 60 min. On-line flue gas analysis, continuous capture of the elutriated fines and analysis of particle size distribution were performed during additional calcium looping tests after sorbent reactivation. Thermogravimetric analysis, scanning electron microscopy and porosimetry were directed to characterize the microstructural features of the spent and the steam hydrated sorbents. Moreover, the different materials were subjected to ex situ impact fragmentation tests. In this way, it was possible to investigate the effect of the hydration time on the following aspects: the changes in the physico– chemical and microstructural properties induced by the hydration treatment; the reactivation of the sorbent CO2 capture capacity; the attrition/fragmentation tendency of the reactivated materials.
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