David Leleu, Andreas Pfennig dleleu@uliege.be
Products, Environment, and Processes (PEPs) Department of Chemical Engineering
Université de Liège
Coalescence Modelling for
Settler Design
agenda
motivation
basic understanding
coalescence modelling
settler simulation
settling of dispersion
stirring-cell experiment
0 5 10 15 20 25 30 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 stirr ing cell h eigh t in m time in ssedimentation curve
coalescence curve
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, t
contactequipment type,
fluid dynamics,
operating conditions
characteristic time
drops need to
coalesce, t
coalescencematerial system,
drop size
modelling coalescence of drops
coalescence probability: fundamental
coalescence probability: fundamental
pnon−coal,Δt = exp −
tcoal
Δt
pcoal = 1− exp −
tcontact
tcoal
pnon−coal = exp −
tcontact
tcoal
∆t
n=tcontact
Δt
tcontact
pnon−coal,nΔt = pnon−coal,Δtn
close-packed zone
drops deformation
counterflow
continuous flow
droplets
εΔh ΔP
hydrostaticΔP
hydrodynamic v
experimental measurement of the holdup
0 10 20 30 40 50 60 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 time in s cell h eigh t in m 0.000 0.1250 0.2500 0.3750 0.5000 0.6250 0.7500 0.8750 1.000 measured hold upsettling simulation
0 20 40 60 80 100 120 20 40 60 80 100 120 140 160 180 c e ll h e ig th i n m msummary
consistent coalescence model
calibrated setup for model validation
purposes
model able to characterize settling
David Leleu, Andreas Pfennig dleleu@uliege.be
Products, Environment, and Processes (PEPs) Department of Chemical Engineering
Université de Liège
