A countercurrent continuous single-stage fluidized bed system using different perforated plate designs was studied. The results indicated that the plate design significantly affected the operation of the countercurrent staged fluidized bed. The triangular hole arrangement plates accumulated more particles above the plates compared to the equilateral square hole arrangement plates at the same operating conditions. When the plate open ratio was increased from 0.37 to 0.4 and 0.44, the size of the operating window increased and the location of the window shifted upward in the solids feeding rate versus superficial gas velocity figure. The increase of the operating window was due to the different discharging mechanisms at different flow regimes. When the position(s) of the large hole( s) was/were moved from the center of the plate to the column wall, the size of the operating window increased. (c) Koninklijke Brill NV, Leiden and Society of Powder Technology, Japan, 2008