Motion of a large object in a bubbling fluidized bed with a rotating distributor

Abstract

a b s t r a c tThis work studies the effect of a low-frequency rotating distributor on the motion of a large object immersed in a bubbling fluidized bed. The object size and density differ from those of the inert solids that conform the bed. Examples of objects moving in a bubbling fluidized bed include passive particles, catalysts and reactants. The rotation modifies the bed dynamics in the surroundings of the distributor and affects the motion of the object within the bed.A set of experiments was carried out in a lab-scale cylindrical bed, equipped with a perforated plate distributor that can rotate at around 1 Hz, for different bed aspect ratios, gas velocities, and object characteristics. Sizes were far larger than that of the solids of the dense phase and densities ranged from half the bed density to values around it. The experiments were video recorded, capturing the surface of the bed from above.As have often been noted, objects might remain in stagnant regions near the distributor and be "lost" or precluded to circulate. This can be avoided in most practical cases forcing the distributor to rotate. Also, the effect of rotation on the circulation time of the objects is presented, showing a general reduction of large circulation times.

Fluidized bed with a rotating distributor operated under defluidization conditions

“…The bubbles were then more homogenously distributed [20] as a consequence of the local structuring of fluidized bed dynamics imposed by the distributor motion at 100 rpm, and the dead zones between holes over the distributor are subse- quently broken improving the radial and axial mixing at the bottom of the bed [21]. Therefore, now the wet regions can be removed from the bottom by the bubble motion facilitating the drying and breakage of the aggregates.…”

“…Furthermore, there is some experimental evidence that the stagnant zones just above the distributor could be broken by the rotating distributor, improving the radial and axial mixing at the bottom of the bed [21]. Therefore, fluidized bed with rotating distributor emerges as a technological solution to be applied in fighting the unwanted defluidization phenomena.…”

Simulation of object motion in a bubbling fluidized bed using a Monte Carlo method

“…The surface of the bed was recorded during 20 min at 30 fps, so the object could be only detected while on the freeboard. A more detailed description of the experimental setup can be found in Soria Verdugo et al (2011c).…”

Optimization of the feeding ports location in a fluidized bed combustor based on Monte Carlo simulations of fuel particles motion

“…For the fuel particle motion inside the bed, the circulation time of a fuel particle during a cycle, from the bed surface to a certain depth and back to the surface, was analyzed experimentally for different operational conditions and fuel particles characteristics in a 3D lab-scale fluidized bed by Ref. [22]. This circulation time was also modeled by Ref.…”