coalescence modelling for design of technical equipment
TRANSCRIPT
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David Leleu, Andreas Pfennig
Products, Environment, and Processes (PEPs)
Department of Chemical Engineering
Université de Liège
www.chemeng.uliege.be/Pfennig
Coalescence Modelling for
Design of Technical Equipment
agenda
motivation
basic understanding
coalescence modelling
settler simulation
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gravity settler
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technical equipment’s
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stirring cell
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stirring-cell experiment
0 5 10 15 20 25 300.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18stirr
ing
ce
ll he
ight
in m
time in s
sedimentation curve
coalescence curve
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effect description influenced by
frequency at which
drops meet
equipment type,
fluid dynamics,
holdup
drops bounce at high
relative velocity
equipment type,
fluid dynamics,
operating conditions
time drops stay in
contact, tcontact
equipment type,
fluid dynamics,
operating conditions
characteristic time
drops need to
coalesce, tcoalescence
material system,
drop size
modelling coalescence of drops
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coalescence probability: fundamental
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pcoalescence,Coulaloglou&Tavlarides = exp −tcoalescence
tcontact
Coulaloglou & Tavlarides, Chem. Eng. Sci., 1977
coalescence probability: fundamental
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pnon−coal,Δt =exp −Δt
tcoal
pcoal = 1−exp −tcontacttcoal
pnon−coal =exp −tcontacttcoal
∆t
n=tcontact
Δt
tcontact
pnon−coal,nΔt = pnon−coal,Δtn
pnon−coal,nΔt =exp −nΔt
tcoal
close-packed zone
drops deformation
film drainage
Arnaud Saint-Jalmes, 2006
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counterflow
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continuous flow
droplets
εΔh ΔPhydrostaticΔPcounterflow v
ΔPtotal = Δphydrostatic -ΔPcounterflow
iso-optical settling experiment
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settling simulation
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0 20 40 60 80 100 120
20
40
60
80
100
120
140
160
180
time in s
ce
ll h
eig
th in
mm
summary
consistent coalescence model
calibrated setup for model validation
purposes
model able to characterize settling
behavior for any system
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David Leleu, Andreas Pfennig
Products, Environment, and Processes (PEPs)
Department of Chemical Engineering
Université de Liège
www.chemeng.uliege.be/Pfennig
Coalescence Modelling for
Design of Technical Equipment