The flow characteristics of fluidized magnetite powder in an inclined open channel

Abstract

The flow characteristics of a fluidized bed of magnetite in an inclined open channel were studied experimentally. Data were obtained on the effects of mass feed rate of solids, channel inclination, superficial gas velocity and channel length on the depths of flowing beds of 139-μm and 169-μm magnetite particles. It was observed that channel inclination and superficial gas velocity have very pronounced effects on the bed depth and shape of the free surface profile of the flowing bed. Under some operating conditions, the flow became unstable, resulting in the formation of flow-rate oscillations. The effect on flow behavior of a narrow defluidized region caused by a discontinuity in the distributor plate was also studied. For certain operating conditions, it was possible to apply the liquid analogy approach, based on the laminar flow of non-Newtonian fluids in pipes, to the flowing bed of magnetite. A friction factor versus generalized Reynolds number correlation, characterized by a power-law model and originally developed for laminar flow of non-Newtonian fluids, showed good agreement with the experimental results. The flowing bed of 139-μm magnetite displayed different non-Newtonian characteristics, depending on the superficial gas velocity and depth of the bed. For a superficial gas velocity of 2.3 u mf and 40 mm bed depth, the flowing bed behaved like a Bingham plastic fluid, while at a 55-mm bed depth it exhibited pseudoplastic behavior.