Reactivation of partially‐sulphated limestone particles from a cfb combustor by hydration

Spent limestone samples from the bed and baghouse of a 22 MWe circulating fluidized bed (CFB) boiler were hydrated and then sulphated in a thermogravimetric analyzer under conditions similar to those found in CFB combustors (850°C, 0.3% SO 2 , 9% O 2 , 9% CO 2 and 81.7% N 2 ). Hydration using water gave faster rates and higher levels of conversion of the residual CaO to Ca (OH) 2 than immersion in pure steam at 150 and 200°C. The particles expanded during hydration and their internal volume increased from 0.1 cm 3 /g Ca before hydration to nearly 0.6 cm 3 /g Ca after dehydration. Hydration rejuvenated the reactivity of the bed material but not that of the baghouse particles. The conversion of Ca to CaSO 4 , in the treated bed particles increased from 32% to over 80% during re‐sulphation.