Numerical and experimental investigation of a countercurrent staged fluidized bed

Fluidized beds are widely adopted as reactors, granulators, or heat/mass transfer units in many industries, including the production of petrochemicals. A countercurrent multi-stage fluidized bed with moderate particle residence time was studied. Horizontal perforated plates were added to section the column and a traditional fluidized bed was modified as the countercurrent continuous multi-stage fluidized bed. Since the diameter of the holes on the plate was about 3 ∼ 4 times larger than the particle diameter, the particles can discharge through the holes and a countercurrent operation was achieved. The bed on the dual flow distributor changed from a non-growing state, a dilute state, a bubbling state to a flooding state with the increase of the gas velocities or the solids feeding flux. A stable bed was presented as an operation map. The operation map is different between a single-stage bed and a two-stage bed and the difference is due to the discharging probability. The particle residence time increased with increasing gas velocity and number of the stages. The addition of a plate increased 40% of the mean residence time. This is an abstract of a paper presented at the AIChE Spring Annual Meeting - The 5th World Congress on Particle Technology (Orlando, FL 4/23-27/2006).