Recycling of fluidized bed combustion ash as a SO2 sorbent: a preliminary investigation of steam hydration/reactivation

Fluidized bed combustion (FBC) processes enable in situ SO2 removal, but generate large amounts of wastes difficult to reuse and landfill. The steam hydration/reactivation of the desulphurizing ability of these ashes is considered a viable recycling pathway. In order to give a contribution to the understanding of the role played by the characteristics of steam-reactivated FBC ashes in the SO2 capture, a lab-scale investigation has been performed to correlate their chemical and physical properties with hydration operating conditions such as temperatures and times. It has been found that the reactivation process, particularly when carried out for 60 minutes at 200°C, was able to give products with an improved overall accessible porosity, induced by both the extent of the reactions and the nature of the hydrated phases (calcium hydroxide and, secondarily, ettringite).