Pressure-drop balance and L-valve performance in a circulating fluidized bed (CFB) were investigated for variation in gas superficial velocity (Ug), secondary air fraction (SA), total solids inventory (Is), and external aeration flow rate (QA), at ambient temperature. The study shows that the solids discharge rate of an L-valve (Gs) changes with the system control variables. Apparently, a wider range of Gs is achieved at increasing Ug, decreasing SA, increasing Is, and increasing QA. The pressure-drop analysis indicates that these characteristics are directly governed by the loop pressure balance. Standpipe bottom pressure is found to be an important indicator of the operating status of the riser, standpipe, and L-valve. The experimental results confirm that an L-valve can be operated effectively by regulating the standpipe bottom pressure. The knowledge obtained from this study is essential for maintaining the performance of a CFB system for combustion operation, as well as for operating circulating fluidized beds on a practical scale. © 2013 Copyright Taylor and Francis Group, LLC