Overall particles flow pattern in a two-zone gas-solid fluidized bed with a secondary-gas stream

Abstract

Fluidized bed reactors with multiple input streams have been developed over the last decades to satisfy industries in the scope of multiphase catalytic reactions, and two-zone fluidized beds have been developed to perform reaction and catalyst regeneration simultaneously. However, the presence of the secondary gas nozzle in the bed significantly impacts the hydrodynamics and efficiency. Particle image velocimetry (PIV) and digital image analysis (DIA) techniques have been used to study different particle flow patterns in a two-zone pseudo-2D fluidized bed with lateral gas injection. The secondary flow nozzles' location has been changed, and different particle flow patterns have been observed in the fluidized bed. It was found that at low excess gas flow rates, when the lateral nozzle is located at the middle part of the bed, particles move downwardly at the bed center and upwardly near the walls; while when the lateral nozzle is located at the top part of the bed, particles have a reverse movement trend. At higher gas velocities for both mentioned nozzle locations, particles move upwardly at the bed center and downwardly near the walls. The formation of large bubbles was less probable when the nozzle was located at the middle of the bed.