In the present investigation, the hydrodynamic study on the four-staged fluidized bed reactor with solid and gas flowing in the counter-current direction has been carried out. The gas phase was air, and the solid phase was amine impregnated activated carbon. By changing the operating condition like weir height, solid flow rate, gas velocity and particle size, pressure drops were determined at the steady and stable operation of the column without loading and flooding. At the low velocity of gas (0.188 m/s) with maximum solid flow rate (4.12 kg/h) and maximum weir height (70 mm), the maximum pressure drop occurred in the column was 220 N/m(2). The minimum pressure drop occurred in the column was 92.2 N/m(2) at high velocity of gas (0.353 m/s), with minimum flow rate of solids (2.15 kg/h) and low weir height of 30 mm. The maximum pressure drop occurred for lowest particle size (467 mu m) at gas velocity (0.309 m/s) was 169.1 N/m(2) at 50 mm weir height and the minimum pressure drop occurred at the same condition for highest size particle size (635 mu m) was 124.8 N/m(2) at the same weir height. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B. V.