The effects of particle size (d(p)) and density on solids recycle characteristics of loop-seal (0.08 m i.d.) have been determined in a circulating fluidized bed (CFB 0.1 m i.d. x 5.3 m high). Five different particles (silica sands and FCC) were used to determine the effects of particle properties on solids recycle characteristics. As the particle size is increased, aeration requirement in the loop-seal increases to attain the same mass flux (G(s)) of silica sands with different size. The effects of aeration rate, particle size, and density on pressure balance around the CFB have been determined. As particle size is increased, solid holdup in the riser decreases at a given G(s) and gas velocity. Pressure drops in the weir section of loop-seal increase with larger and denser particles. In the vertical aeration section, pressure drop increases with decreasing particle size and increasing particle density. Split of vertical aeration to the downward direction increases with increasing G(s). The pressure drops across the loop-seal have been correlated with the modified Froude, Reynolds numbers, and the density ratio of gas and solid.