Investigation of Particle Motion in a Swirling Fluidized Bed using Particle Imaging Velocimetry

Fluidized bed is an advanced technology which possesses a number of
characteristics ideal for a wide variety of industrial applications due to its advantages
over many existing technologies in industry. However, conventional fluidized bed
used in most of the industry today has certain drawbacks which affect the efficiency
of the bed. Swirling Fluidized Bed (SFB) is one of the evolutions of fluidized bed,
which has the potential for solving many drawbacks of conventional fluidized bed.
Nonetheless, limited research has been done on this bed as compared to other
versions of fluidized bed, thus a lot of problems occurred when come to scaling up to
commercial size. This was mainly due to the lack of understanding of the particle
dynamic characteristics of the bed. Most of the research studied the overall bed
characteristics especially the pressure drop. There is limited study on the velocity and
particle motion. Furthermore, available literature concentrates only analytical model
and simulation results. No published experimental information is available for the
analysis of the particle velocity. Thus, the objectives of the present study are to
investigate particle motion in a swirling fluidized bed and to study the effect of air
flow rate, bed weight, blade angle, particle size and particle shape on the fluidized
particle velocity. The particle motion of the SFB is studied by using Particle Imaging
Velocimetry (PIV) in an experimental model of SFB. The experiments were carried
out with bed weight varied from 500 g to 1500 g with only stable swirling regime
was studied and the velocity of the top layer particles was evaluated. From the study,
it is found that the particle velocity increases with air flow rate at shallow bed and as
bed weight is increased, particle velocity decreases by higher occurrence of vigorous
bubbles. It is also observed that particle velocity decreases less than 18% with 3o
increment in the blade angle. Small particle yields lower minimum swirling air
superficial velocity which means preferable for saving energy, but with constraint of
shallow bed. Particle with elongated shape possesses short range of stable swirling
due to easier occurrence of bubbling. The results of this project give a better
understanding of the particle velocity and motion which can provide a great
contribution towards designing the fluidized bed especially for catalyst activity,
coating and drying.