ATTRITION AND CHANGES IN PARTICLE-SIZE DISTRIBUTION OF LIME SORBENTS IN A CIRCULATING FLUIDIZED-BED ABSORBER

The attrition data of calcium oxide pellets in a circulating fluidized bed absorber (CFBA) are presented with a modified second-order attrit ion model incorporating an asymptotic minimum bed weight and an excess gas velocity from the minimum fluidization. Two sizes (903 and 1764 m u m) of calcium oxide pellets are fluidized with several superficial g as velocities. The experimental attrition rate constants obtained from the attrition model are used to fit a modified Arrhenius equation, wi th a pseudo activation energy term proportional to the excess fluidizi ng energy. The model with the measured rate constants for single-parti cle 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 ap plicable for batch and continuous operations of fluidized beds in whic h size reduction predominantly results from attrition and elutriation frequently seen in a fast fluidized bed and in a circulating fluidized bed.