Mathematical models Of SO2 capture by uncalcined limestone (CaCO3) particles with solid attrition were compared under pressurized fluidized bed combustion conditions. For reaction, we used: (1) a shrinking core model with a distinct border between the product (CaSO4) layer with a conversion of unity and unreacted core with a conversion of zero, and (2) a distributed reaction model with smooth transition from the unreacted part to the product part with conversion between zero and unity. Continuous attrition and intermittent attrition were compared for attrition. Apparent conversion of the solid was overestimated regardless of the reaction model for continuous attrition. Attrition model plays an important role in determining limestone utilization efficiency, whereas the reaction model played only a minor role. (C) 2003 Elsevier Science Ltd. All rights reserved.