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Experimental Study of Conical Fluidized
Bed Using Radioisotope Based Techniques
Lipika Kalo1, H.J.Pant2, and Rajesh K. Upadhyay1
1: Chemical Process Engineering Laboratory (CPEL)
Department of Chemical Engineering
Indian Institute of Technology Guwahati, Assam, India
2: Isotope and Radiation Application Division
Bhabha Atomic Research Centre, Mumbai, India
ID: B01-02
Advantage of Conical Fluidized Bed over Cylindrical Fluidized bed
Applications
Drying
Granulation
Food processing
Coking
Nuclear fuel
particle coating
Crystallization
Gasification and
liquefaction of
coal
Issues• Entrainment
• Poor mixing
• Non-uniform
particle
distribution
• Increases power
requirementGasGas
Peng et al., Chemical Engineering Science, 52(14), 2277-2290 (1997).
Gas
Fixed bed
Gas
Turbulently Fluidized Bed
Gas
Transition Regime
Gas
Partially Fluidized bed
Gas
Fully Fluidized Bed
Increasing velocity
Regimes in Mono Conical Fluidized Bed
Regimes in Binary Conical Fluidized BedComplete
SegregationIncomplete Segregation
Heterogeneous Mixing
Homogeneous Mixing
Increasing velocity
0.6 mm glass particle
1 mm glass particle
Radioactive Particle Tracking (RPT)➢ A gamma ray emitting radioactive particle is
used
➢ Particle resembles the shape, size and densityof the phase of interest
➢ Particle is allowed to move freely inside thecolumn
➢ An array of scintillation detector are placedoutside the vessel of interest to record theintensity of radiation
➢ By using reconstruction algorithm andexperimental data the instantaneous positiontime series of the particle is measured
➢ Instantaneous velocity is calculated by timedifference of two successive position ofparticle.
➢ From the Instantaneous velocity time series arich data base is calculated by applyingsuitable post processing.
Flow chart of Radioactive Particle Tracking (RPT)
RPT Experiments (counts from detector)
Instantaneous Position of the Particle
Instantaneous velocity (time differentiation of two successive position)
Ensemble Average Velocity
Fluctuation Velocity
ReconstructionAlgorithm
Calibration (Distance count map)
Eulerian grid
Limtrakul et al., Chemical Engineering Science, 60, 1889–1900 (2005).
r, θ
r, z
i, j, ki, j, k+1
i, j, k+2
RMS velocities, Kinetic Energy of fluctuation, Granular temperature, diffusivity etc.
Quantities Obtained from RPT Experimental Data
Instantaneous Velocity
Ensemble average velocity
Fluctuating velocity component
RMS velocity
Stress
Fluctuating kinetic energy per unitvolume
Granular Temperature
z
zv
t
( , , )
,
1
1( , , ) ( , , )
( , , )
N i j k
q q n
n
v i j k v i j kN i j k
' ( , , ) ( , , ) ( , , )q q qv i j k v i j k v i j k
'2RMS
q qv v
' '( , , ) ( , , )qs p q sv i j k v i j k
'2 '2 '21[ ]
2p r zKE v v v
2
3s sk
Ks= Kinetic Energy due to solid velocity fluctuation per unit mass
Experimental Setup
Material Size of Solid Umf (m/s)
Glass beads 1mm 1.97
Glass beads 0.6 mm 1.1
Bed Composition Liquid
Velocity
(m/s)
100% 1mm 2, 3, 4Umf
50% 1mm and 50% 0.6mm 2, 3, 4Umf
100% 0.6 mm 2, 3, 4Umf
Sc-46 is used as a gamma-ray sourceActivity = ~ 300 microCi
Tracer particle
Effect of Gas Inlet Velocity on Mean Axial Solid Velocity
Mono 1 mm Glass
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 1
mm
so
lids
[m/s
]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 1
mm
so
lids
[m/s
]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=2Umf
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 1
mm
so
lids
[m/s
]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=3Umf
• h represents the static bed height=25 cm
• Observed upward motion of solid particles inthe center and downward motion near thewall
• Increase in velocity increases the solid axialvelocity as the momentum through the liquidincreases
• Velocity of the solid increases with the height
Effect of Gas Inlet velocity on Mean axial solid velocity
Mono 0.6 mm Glass
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 0
.6m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=2Umf
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 0
.6m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 0
.6m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=3Umf
• Same trend observed for both 1mm and0.6 mm particle
• Velocity of bigger particle is lower thansmaller particle for a particular velocityas both the bed have been operated atsame velocity
Mean axial velocity ofbinary fluidized bed
50% 1mm-50s 0.6 mm Glass beads
• For binary mixture velocity profile is same as of mono dispersed bed
• With increse in level inside the bed solid velocity increases which shows thattop section is more violent compared to bottom section
• In binary bed the velocity of bigger particle is higher as compared to unary bedof same size it means smaller particles helps the fluidization of bigger particles
• Homogeneous distribution and mixing of solids are not observed
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 1
mm
so
lids
[m/s
]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 0.2 0.4 0.6 0.8 1
Vz
me
an o
f 0
.6m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1
Vz
rms
of
1m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1
Vz
rms
of
0.6
mm
so
lids
[m/s
]r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
• With increase in air velocity fluctuation at the top section increases andbed become more violent for both the particles
• Fluctuation in smaller particle is higher than bigger particle as the u/umf ofsmaller particle is higher than bigger particle.
• Similar trend is observed for all the air inlet velocities
RMS velocities in mono dispersed bed of two different sizes
Mono Bed 1 mm Glass beads Mono Bed 0.6 mm Glass beads
RMS velocities in binary bed of 50% 1mm and 50% 0.6 mm particle
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1
Vz
rms
of
1m
m s
olid
s [m
/s]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1
Vz
rms
of
0.6
mm
so
lids
[m/s
]
r/R [-]
0.25h expt
0.5h expt
0.75h expt
U=4Umf
• Profile of axial rms velocity remains same for binary and mono dispersed bed
• fluctuation in smaller particle is only marginally higher than bigger particle in binarybed.
• However compared to mono bed of smaller particle fluctuation in binary bed is lowerwhich confirms that smaller particles are transferring some of the momentum tobigger
Conclusions➢Velocity of solid increases with increase in fluid velocity in conical
bed
➢Axial mean velocity of bigger particle is lower than smallerparticle for a particular gas velocity as both the bed are operatedat same velocity
➢The fluctuation in case of smaller particle is more than biggerparticle which is expected as smaller particle bed is operated athigher u/umf ratio
➢ Increase in fluctuation for bigger particle in binary bed isobserved which confirms that smaller particles transfer some ofits momentum to bigger particle to ease the fluidization.
➢Homogeneous distribution of particle is not observed even at avelocity of 4umf of bigger particle
➢These information are very critical for designing the industrialcoater
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