The attrition data of calcium oxide pellets in a circulating fluidized bed absorber (CFBA) are presented with a modified second-order attrition model incorporating an asymptotic minimum bed weight and an excess gas velocity from the minimum fluidization. Two sizes (903 and 1764 mu m) of calcium oxide pellets are fluidized with several superficial gas velocities. The experimental attrition rate constants obtained from the attrition model are used to fit a modified Arrhenius equation, with a pseudo activation energy term proportional to the excess fluidizing energy. The model with the measured rate constants for single-particle size is used to predict the changes in size distribution in a bed with a mixture of various particle sizes. The present method may be applicable for batch and continuous operations of fluidized beds in which size reduction predominantly results from attrition and elutriation frequently seen in a fast fluidized bed and in a circulating fluidized bed.