The efficiency of limestone utilisation for sulphur capture in fluidised bed combustors (FBC) is low due to incomplete sulphation of CaO. The disposal of the spent sorbent is problematic and costly. Reutilisation of the spent sorbent is highly desirable both in terms of improving overall plant economics and process efficiency. In this work, wet grinding of the bottom ash from a CFBC unit was used to reactivate the spent ash. The ash was then reinjected into a CFBC pilot plant and the performance of sulphur capture was compared with that of limestone. The activated ash showed higher sulphur capture efficiency, which is attributed to the more porous structure or larger specific surface area of the particles of the ash brought about by hydration of CaO and the subsequent dehydration of Ca(OH)(2). The kinetics related to sulphur capture and the wet grinding process are also discussed. (C) 2003 Elsevier Science B.V. All rights reserved.