Hydrodynamic characteristics of tapered fluidized beds differ from that of conventional columnar beds by the fact that a velocity gradient exists along the axial direction of the bed. To study the characteristics of tapered beds, several experiments have been carried out with different tapered angles of the bed, with regular as well as irregular particles of different sizes and densities. The tapered angles of the beds have been found to affect the characteristics of the bed. Models based on dimensionless analysis have been proposed to predict the minimum fluidization velocity and maximum pressure drop for gas-solid tapered fluidized beds. Experimental values of minimum fluidization velocity and maximum bed pressure drop with air as the fluidizing medium compare well with that predicted by the proposed models. The results have also been compared with other models available in the literature. (c) 2007 Elsevier B.V. All rights reserved.