Institut für Sicherheitsforschung
A study on the mixing behaviour of different densities liquids in a
stirred tank by passive and reactive tracers
H.V. Hristov, G. Hessel, H. Kryk, H.-M. Prasser, W. Schmitt
Objectives and model development
Experimental set-up
General modelling approach
•Theoretical assessment of the
stirred tank reactor performance via
CFX.
full three dimensional approach
impeller delay in reaching the target
rotating speed modelled
gas phase involved
ƒ
ƒ
•Development of CFD codes
coupled with chemical reaction and
multiphase flow models for
ƒ
CFX Numerical models
• Scale-up
• Optimisation
• Hazard analyses
transparent heavier
liquid (water)
Free Surface Model
Multicomponent Model
Buoyant Flow
Sliding Mesh
Fluid dependent k-Epsilon
turbulence model
ƒ
ƒ
ƒ
ƒ
ƒ
coloured layer
of a lighter liquid
(isopropanol)
Pfaudler
impeller
Simulation results
Passive tracer mixing
Integral mixing curves at different positions
Dynamic mixing of Initially stratified
different density liquids
The experimental ones were obtained by digitally processing the video images.
The averaged concentration values at the given points were used for the theoretical mixing curves.
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wall
centre
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IP concentration, [-]
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HCl
→
dissolved in
water
NaCl
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time, [s]
time,
[s]
time,[s][s]
time,
NaOH
+
dissolved in
isopropanol
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wall
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time, [s]
Reactive tracer mixing
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simulation
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time, [s]
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experiment
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time, [s]
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experiment
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Free surface deformation
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centre
IP concentration, [-]
IPconcentration,
concentration,[-][-]
IP
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simulation
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time, [s]
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simulation
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2s⇒
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wall
centre
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IP
concentration,
IP concentration,
[-] [-]
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IP concentration, [-]
IP
[-][-] [-]
IP
IPconcentration,
concentration,
concentration,
1s⇒
wall
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1
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centre
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concentration,
IPIPconcentration,
[-] [-]
0,5 s ⇒
IP concentration, [-]
1
+
H2O
simulation
experiment
simulation
experiment
1.5 [s]
simulation
2.5 [s]
experiment
simulation
experiment
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simulation
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Conclusions and further work
Further work
•
ƒ numerical simulation of gas-liquid
mixing
Good agreement between the
experiments and the simulations
Mixing curves
Free surface
•
Higher mixing rates predicted
•
Improvements of the experimental
technique are required
•
Good agreement for up to 2.5 s in
the case of reactive tracer mixing
Ansprechpartner:
Dr. H.V. Hristov
Dr. H. Kryk
FZ Rossendorf
Tel. (0351) 260 - 2192
Tel. (0351) 260 - 2248
Postfach 51 01 19
ƒ example: experimental observation
using X-Ray cone beam tomography
ƒ introduction of reaction kinetic models of complex reactions into CFD model
ƒ precondition:
investigation of reaction pathways and setup of complex kinetic models using
reaction calorimetry and chemical online analytical instruments
model validation
RC1 + online FTIR
150
development of
reaction kinetics
A+B → C+D
stirrer speed
[email protected]
[email protected]
01314 Dresden
r =k
0

 −E

A 

 R ⋅T 
 ⋅ [A] n ⋅ [B] m
⋅e
heat
release rate [W]
Reaktionsleistung
[W]
Conclusions
T=
T=
T=
T=
100
40°C
50°C
60°C
70°C
50
0
0
50
100
150
200
Zeit [min]
time
[min]
Mitglied der Leibniz-Gemeinschaft
www.fz-rossendorf.de
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