The fluidization quality and gas back-mixing property in a two-dimensional and a large-scale three dimensional gas-solids fluidized beds of FCC particles were compared in the range containing both bubbling and turbulent flow regimes.The experimental results indicated bed shape’s sound effects on fluidized beds of Geldart A particles.The hydrodynamics and gas-solids mixing demonstrated both similar and different properties in the two-dimensional and three dimensional beds.The bed expansion with increasing superficial gas velocity showed similar trends in both beds.However

the fluidization quality and axial gas dispersion coefficient were much lower in the three-dimensional beds.Moreover

there were different trends of pressure fluctuation and axial gas dispersion coefficient with increasing superficial gas velocity and even different gulf streaming patterns in the two beds.In general

it can be concluded that the two-dimensional bed in this study represented a small-scale bed with strong wall effect

while the three-dimensional bed represented a large-scale bed with strong effect from static bed height.