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Abstract:
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The thesis presented here unveils an experimental study of the hydrodynamic
characteristics of swirling fluidized bed viz. pressure drop across the distributor and the
bed, minimum fluidizing velocity, bed behaviour and angle of air injection. In swirling
fluidized bed the air is admitted to the bed at an angle 'Ѳ' to the horizontal. The vertical
component of the velocity v sin Ѳ causes fluidization and the horizontal component
v cos Ѳ contributes to swirl motion of the bed material.The study was conducted using spherical particles having sizes 3.2 mm, 5.5 mm & 7.4
mm as the bed materials. Each of these particles was made from high density
polyethylene, nylon and acetal having relative densities of 0.93, 1.05 and 1.47
respectively.The experiments were conducted using conidour type distributors having four rows of
slits. Altogether four distributors having angles of air injection (Φ)- 0°, 5°, 10° & 15°
were designed and fabricated for the study. The total number of slits in each distributor
was 144. The area of opening was 6220 mm2 making the percentage area of opening to
9.17. But the percentage useful area of opening of the distributor was 96.The experiments on the variation of distributor pressure drop with superficial velocity
revealed that the distributor pressure drop decreases with angle of air injection.
Investigations related to bed hydrodynamics were conducted using 2.5 kg of bed
material. The bed pressure drop measurements were made along the radial direction of
the distributor at distances of 60 mm, 90 mm, 120 mm & 150 mm from the centre of
the distributor. It was noticed that after attaining minimum fluidizing velocity, the bed pressure drop increases along the radial direction of the distributor. But at a radial
distance of 90 mm from the distributor centre, after attaining minimum fluidizing
velocity the bed pressure drop remains almost constant. It was also observed that the
bed pressure drop varies inversely with particle size as well as particle density.An attempt was made to determine the effect of various parameters on minimum
fluidizing velocity. It was noticed that the minimum fluidizing velocity varies directly
with angle of air injection (Φ), particle size and particle density.The study on the bed behaviour showed that the superficial velocity required for
initiating various bed phenomena (such as swirl motion and separation of particles from
the cone at the centre) increase with increase in particle size as well as particle density.
It was also observed that the particle size and particle density directly influence the
superficial velocity required for various regimes of bed behaviour such as linear
variation of bed pressure drop, constant bed pressure drop and sudden increase or
decrease in bed pressure drop.Experiments were also performed to study the effect of angle of air injection (Φ). It was
noticed that the bed pressure drop decreases with angle of air injection. It was also
noticed that the angle of air injection directly influence the superficial velocity required
for initiating various bed phenomena as well as the various regimes of bed behaviour. |