An experimental study was conducted in a large scale circulating fluidized bed (0.3 m diameterx15.5 m tall) equipped with nonmechanical L-valve (0.25 m diameterx1.52 m long) varying the riser superficial gas velocity (U-g), bed inventory (m), L-valve aeration velocity (U-Lvalve), and standpipe aeration velocity (U-more). The effects of these operational parameters on pressure drop were investigated in each of the different components in the CFB and on the solid circulation rate with two different Group B particles (180 mu m glass bead and 750 pm phosphorescent polyethylene beads, PPE). Tests were carried out at ambient temperature and pressure conditions using air as the fluidization gas. The operating parameters were shown to significantly affect pressure drops across various sections of the CFB due to redistribution of solids within the system. The pressure drop in the horizontal section of the L-valve was affected by aeration rates in addition to the solid flow rate reported in previous studies of smaller L-valves without aeration. A new dimensionless semi-empirical correlation was able to explain >98% of the variance between pressure drop across the horizontal section of the L-valve and operating parameters for these Group B particles. The results of present study indicated that the nonmechanical L-valve cannot be isolated from the CFB system for performance evaluation. Published by Elsevier B.V.