The effect of level of the overflow outlet for continuous flow of solid particles on the pressure drop of a bubbling fluidized-bed that employed an in-bed inlet for solid feed was investigated with changing solid properties, solid feed rate, gas velocity, and level of the overflow outlet. The pressure drop of fluidized-bed (Delta p(bed,f)) decreased with increasing gas velocity, but increased with either solid feed rate or level of the overflow solid outlet (L). The Delta p(bed,f)/L increased with L. Irrespective of particle size and density, bed height converted for minimum fluidization condition (pressure head by bed weight, H-mf,H-f) decreased with increasing the volume flow rate of bubble but increased with either the solid feed rate or the level of the overflow solid outlet. The nominal vertical height, height between the H-mf,H-f and the level of the overflow outlet, that bubbles transported particles while drawing the solid particles out of the fluidized-bed increased as either the volume flow rate of bubble or level of the overflow outlet increased. However, it decreased as the solid feed rate increased. It appeared that the power of bubble for lifting solid to be discharged through the overflow outlet was same at the fixed volume flow rate of bubble, solid feed rate, and level of the overflow solid exit. The power of bubble increased with the level of the overflow outlet but not linearly. The correlation proposed for the pressure drop across the bubbling fluidized-bed was useful to predict the pressure drop across the recycle chamber of the loop seal and the external solid circulation rate in the circulating fluidized-bed system. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.