Effect of inclined distributor on the motion behavior of a large spherical object in the bottom zone of a fluidized bed

• Effect of inclined angle on the residence time of objects is quantified.
• Object is much larger and denser than the coexisting fine particles.
• Gas–solid flow dynamics with various inclined angles are compared.
• Characteristic of the force acted on stagnant object is addressed and analyzed.

In many applications of the fluidized bed, large and dense objects may be captured in a stagnant zone over the air distributor, having paramount influence on the performance of the bed. Inclined air distributor was commonly used to induce the objects to the discharging hole, ensuring the normal operation of this type of fluidized bed.A set of experiments was carried out to study the residence time distribution (RTD) of the large objects in four lab-scale fluidized beds, each equipped with a certain inclined angle of the air distributor, for various fluidizing velocities. The objects were far larger than the fine particles of the dense phase and their densities ranged from 2 to 3.5 times of the fixed bed density. Results show that increasing the inclined angle decreases the residence time of the object in a fluidized bed, and the effect becomes significant at a low fluidization velocity. Numerical simulations based on Eulerian–Eulerian model were taken to investigate the characteristic of the dynamic force acted on the stagnant objects over the air distributors. It indicates that the transverse bubble and particle movements due to the existence of the inclined air distributor and the oriented air caps primarily cause the periodical force fluctuation on the object along the inclination direction. The drag force and buoyancy force acted on the object from the surrounding gas–solid flow and the friction force from the distributor vary with the inclined angles, resulting in larger motion velocities and longer residence times for the objects in the fluidized beds with small inclined angle distributors.

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