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, tcontact equipment type, fluid dynamics, operating conditions characteristic time drops need to coalesce, tcoalescence material system, drop size
modelling coalescence of drops
close-packed zone
drops deformation
film drainage
counterflow
continuous flow
droplets
εΔh ΔP
hydrostaticReDrop (Representative Drop) simulation
definition of the system
•
material properties•
simulation parameterstime loop
local holdup evaluated for each height element
drop loop
•
drop velocity•
update of the vertical position of each dropexperimental 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
simulation tool based on ReDrop
model able to characterize settling
David Leleu, Andreas Pfennig dleleu@uliege.be
Products, Environment, and Processes (PEPs) Department of Chemical Engineering
Université de Liège
Coalescence Modelling for
Settler Design
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
