Hydration-induced reactivation of spent sorbents for fluidized bed calcium looping (double looping)

The aim of this work was to study the hydration-induced reactivation of spent sorbents from a calcium looping process. The changes of the sorbent properties induced by hydration, the regeneration of the CO2 capture capacity and the attrition tendency of the material once reused in the looping cycle were investigated. To this end, a reference limestone was subjected to multiple calcination/carbonation cycles in a lab-scale fluidized bed reactor and then reactivated by water hydration at room temperature for different times. Results suggested that the sorbent under investigation should be hydrated for times as short as possible compatible with complete chemical hydration. In fact, long hydration times bring about cramming (chemical sintering) phenomena, lower enhancement in the active porosity, increased attrition tendency and reduced reactivation. Attrition/fragmentation data referring to as-received and reactivated sorbents were compared. Relationships among CO2 capture capacity, surface properties and attrition tendency were presented and critically discussed, taking into account also the results obtained for a different sorbent.