An experimental study was performed on the attrition of the bed materials in a recirculating fluidized bed (RCFB) using Indian standard (IS) grade I sand (size between 2.0 and 1.0mm) at ambient conditions. Experiments were performed with superficial air velocity ranging from 7.13 to 9.16m/s, bed inventory of 7-10kg, and a spacing of 0.085m between the jet top and draft tube bottom. The main objective of the study was to investigate the effects of operation time on the attrition and size distribution of sand particles in a RCFB. It was noticed that the prime mode of attrition of bed materials was abrasion, not fragmentation. Reduction in the downcomer bed height was observed with increasing operation time. It indicates that attrition was significant and fines were elutriated out with the fluidizing air. Furthermore, variations in the shape, size, and harmonic diameter of particles were studied with increasing operation time. It has been observed that the coefficient of uniformity and coefficient of curvature showed increasing patterns. It specifies that particles of different size ranges and fines were formed due to attrition of particles. At the end of the operation, it was found that a significant amount of fines was elutriated with fluidizing air from the reactor.