Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: 9.7.1 - Investigation of Binary Droplet-Coalescence in Liquid-Liquid-Systems
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 Material Information
Title: 9.7.1 - Investigation of Binary Droplet-Coalescence in Liquid-Liquid-Systems Collision, Agglomeration and Breakup
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Eiswirth, R.T.
Bart, H.-J.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: binary-coalescence
high-speed
droplet-droplet-coalescence
zeta potential
capillary waves
 Notes
Abstract: The present work will overviews different investigations dealing with droplet-droplet-coalescence. The different investigation methods are linked to each other by the coalescence efficiency of droplets in liquid-liquid-extraction (LLE). The coalescence efficiency (e.g. in the coalescence kernel in droplet population balance models), which is used for modeling LLE-columns, is a central variable. Despite these important role, the droplet-coalescence is not yet fully understood and current models usually based on use fitting parameters to describe the influence of the multiple parameters such as mass transfer, pH-value or the concentration of salts on the droplet coalescence. Better understanding of the droplet-droplet-coalescence and more information with respect to simulations are the main aims of the presented work. Therefore, the droplet-droplet-coalescence itself was investigated by means of high-speed-films. Different aspects of the phenomena are presented in detail. In addition, zeta potential measurements in ultra-pure and surfactant free systems were performed and the results were compared with the binary coalescence probabilities, obtained by binary droplet experiments of free rising droplets in ultra-pure systems.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
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7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


Investigation of Binary Droplet-Coalescence in Liquid-Liquid-Systems


R.T. Eiswirth* and H.-J. Bart*

Faculty of Mechanical & Process Engineering, Chair of Separation Science and Technology,
University of Kaiserslautern P.O.B. 3049, 67653 Kaiserslautern, Germany
eiswirth@mv.uni-kl.de and bart@mv.uni-kl.de
Keywords: binary-coalescence; high-speed; droplet-droplet-coalescence; zeta potential; capillary waves;




Abstract

The present work will overviews different investigations dealing with droplet-droplet-coalescence. The different
investigation methods are linked to each other by the coalescence efficiency of droplets in liquid-liquid-extraction
(LLE). The coalescence efficiency (e.g. in the coalescence kernel in droplet population balance models), which
is used for modeling LLE-columns, is a central variable. Despite these important role, the droplet-coalescence is
not yet fully understood and current models usually based on use fitting parameters to describe the influence of
the multiple parameters such as mass transfer, pH-value or the concentration of salts on the droplet coalescence.
Better understanding of the droplet-droplet-coalescence and more information with respect to simulations are the
main aims of the presented work. Therefore, the droplet-droplet-coalescence itself was investigated by means of
high-speed-films. Different aspects of the phenomena are presented in detail. In addition, zeta potential measurements
in ultra-pure and surfactant free systems were performed and the results were compared with the binary coalescence
probabilities, obtained by binary droplet experiments of free rising droplets in ultra-pure systems.


Nomenclature


Roman symbols
d diameter (m)
h collision rate (-)
t time (s)
v velocity (nms1)
x size (prm)
N number (-)
Q (1) cumulative size distribution
Greek symbols
A coalescence probability (-)
w coalescence rate (-)
( zeta potential (rnV)
Subscripts
cap capillary wave
coal coalescence
i group
int interaction
p particle


Introduction

Liquid-liquid extraction processes are especially ap-
plicable with thermo-sensitive or non volatile solutes
and offering high throughputs at low energy consump-
tion. Therefore, these processes are well established and
widespread in industry. In spite of the mature unit oper-
ation, there is still a demand for research. Especially
in predicting a column behavior. Moreover, in order
to minimize costly and time-consuming pilot plant ex-
periments model-based simulations are of limited value,
when they rely on adjustable parameters.
The coalescence phenomena is one of the crucial pro-
cesses in liquid-liquid-extraction. However the phe-
nomena is not fully understood and modeled by semi-
empirical concepts (Gomes et al. (2004), BlaB (1988)).
The droplet-droplet coalescence and the coalescence at
planar boundaries (e.g. settling zones) are the two dis-
tinguished coalescence mechanisms in liquid-liquid sys-
tems. Decisive for the efficiency and productivity of an
extraction column are especially the droplet-droplet co-
alescence in the active zones during mass transfer and
in the phase separator (Gross et al. (2002), Klinger et al.
(2002), Kraume et al. (2004)). The droplet-droplet co-
alescence is affecting the hydrodynamics in extraction







7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


columns by changing the droplet size distribution. The
coalescence process itself is very sensitive to changes
in local chemical composition (Simon and Bart (2002)).
Ions which are adsorb at the liquid interface inducing
electrostatic interactions and influence the coalescence
process. Therefore, the data of the chemical system,
such as viscosity, density and surface tension are not
sufficient enough to describe the properties of the sys-
tem. Furthermore, both mass transfer direction and sur-
factants are influencing the droplet coalescence and can
not be neglected (Rommel et al. (1992)). These multiple
influences are usually not adequate implemented in the
models, which can be classified into two groups (Tobin
and Ramkrishna (1992), Pfennig and Schwerin (1998),
Tobin and Ramkrishna (1999), Henscke et al. (2002)).
The first group are fully empirical approaches (Kentish
et al. (1998), Wright and Ramkrishna (1994)) and to the
second belongs the semi empirical models (Coulaloglou
and Tavlarides (1977), Sovova (1981)). For calculating
the coalescence rate (w), a product of the collision rate
(h) and coalescence efficiency (coalescence probability)
(A) of two droplets with the diameters dl and d2 are of-
ten used in the models.

W(dl,d2) = h(d,d2) A(did2) (1)
Correlations describing the coalescence behavior are
often estimated in stirred vessels (Gabler et al. (2005),
Ruiz and Padilla (2005), Alopaeus et al. (2002), Pod-
gorska and Baldyga (2001)) and fitting parameters have
to be used to characterize the influences of the chemi-
cal system. Due to neglecting the influences of the ba-
sic phenomena, the correlations are only valid for one
chemical system or apparatus geometry.
Studies in gas-liquid (Millies and Mewes (1996)) and
fewer in liquid-liquid-systems (Pfennig and Schwerin
(1998), Tobin and Ramkrishna (1999), Ritter (2002))
show the influence of electrolytes on the coalescence and
thus affecting mass transfer considerably. Admixture of
sodium chloride or sodium bromide of a concentration
of 1 mol/m3 changed the coalescence time up to three
order of magnitudes. Big changes of the coalescence
probability were reported from Tobin et al. (1990) by
raising the pH-value at a low ionic strength. At a higher
pH-value, the adsorption of hydroxide ions increases at
the interface causing raising the surface potential. The
induced electrostatic double layer (Ster (1924)) repels
the droplets and hinders coalescence. Meanwhile, addi-
tions of salts have then a converse effect. As a result of
the high ionic concentration in the aqueous phase, the
electric double layer at the surface is getting smaller ac-
cording to DLVO-theory (see in Meyers (1991)). So
the surface potential gets lowered and the coalescence
barrier reduce. This phenomena depends on the ionic
species, ionic strength and pH-value and is reflected by


the zeta potential.

Experimental Method


Chemical system:
The standard test system toluene/acetone/water,
which is recommended by the European Federation of
Chemical Engineering Misek (1985), was used for the
investigation of the coalescence and zeta potential be-
havior. The system is commonly used for testing the
performance of liquid-liquid extraction columns and due
to the large available database in literature.
Due to the sensitivity of the coalescence process to
changes in the chemical system, the chemicals used were
AnalaR grade and the organic phases were distilled to
remove ionic and metallic contaminations. Bidistilled
water with a conductivity of <0.5 pS/cm was used for
preparing the aqueous phase. To reduce the influence of
trace gases on the system (e.g. carbon dioxide), water
was degassed before use.
Sodium hydroxide and sulphuric acid were used to
adjust the pH-value in accordance to the salt species
used (AnalaR grade Na2SO4) when adjusting the ionic
strength of the solution. Both phases were saturated mu-
tually in a stirred tank for at least 24 h to avoid mass
transfer that leads to side effects, e.g. Marangoni con-
vection. To limit the influence of contaminations, an
extensive cleaning procedure for all parts of the experi-
mental set-up in contact with organic or aqueous phase
was performed.
Experimental setup:
In this work, an experimental setup (Fig. 1) was de-
veloped based on the setup presented by Eiswirth et al.
(2008). Special attention was paid to the dimensions,
wall thickness of the measuring cell, the temperature
regulation and the light intensity. The small-scale mea-
surement cell is one of the features of the setup, which
help in maintaining the temperature constant during the
experiment. The wall thickness of the measurement cell
was minimized to avoid light scattering and, in this way,
to increase the light intensity leading to more accurate
results.
The experimental setup consists of a high intensity
light source (1) (Dedocool COOLH). The emitted light
is homogenized by a diffuser (2) mounted in front
of the measuring cell (5) which contains the heat ex-
changer (3) and the droplet catcher (4). The move-
ment of the droplets is captured by a high-speed cam-
era (7) (Photron ultima APX-RS; 10-bit monochrome
CMOS sensor, 17 pm pixels; up to 3.000 fps at full 1,024
x 1,024-pixels resolution; 10,000fps at 512 by 512-
pixels). Connected to a macro-objective (6). The im-
ages are stored in the internal memory of 2 GB and then
transferred to a PC for further analysis. The drops can be






















Figure 1: Experimental setup for velocity and shape
measurements of single rising droplets.
(A) capillaries, (B) main connectors, (C)
capillary-gasket, (D) gasket, (E) plug, (F)
connectors to pumps, (G) outlet, (1) high in-
tensity light source, (2) diffuser, (3) heat ex-
changer, (4) droplet catcher, (5) measuring
cell, (6) macro-objective, (7) high-speed cam-
era.


produced continuously using different types of capillar-
ies (A) directed towards each other being fed from two
pulsation-free metering pumps. By using such pumps,
the oscillation of the droplets occurring when they de-
tached from the capillary tip reduces. Due to the high
In.igilk.lilnii and high time resolution of the experi-
mental setup, the behavior of the rising droplets can be
observed in details.
Experimental procedure:
The electrophoretic light scattering method was ap-
plied to determine the zeta potential using an ELS-
800 by Otsuka electronics (Osaka/Japan). The charged
droplets were temporary accelerated by a DC voltage.
Thereafter their velocity is calculated by the Doppler
shift of the modulated scatter light signal from the probe
and reference beam and then converted in the elec-
trophoretic mobility. Turbidity of the specimen due to
the higher content of the organic phase is resulting in
a blurred detection of the scattering signal (Oka et al.
(1990)). Therefore, this method is applicative only for
diluted solutions and small particles.
Small particles can be easily obtained in surfactant
stabilized systems. Compared to this, measurement of
the zeta potential is tricky in surfactant free systems due
to the easy breakdown of the dispersion. Therefore,
several methods for creating a suitable dispersion for
the zeta potential measurements were evaluated. Com-
pared to other methods (e.g. high-speed mixing with
an Ultra-Turrax, IKA Werke GmbH & Co. KG), the
best method for creating suitable dispersions was a rapid
quenching method presented by Marinova et al. (1996).
It was adapted in terms of temperature gap and time
of saturation. For creating the dispersions, the param-
eters of the ih l6cli, aqueous solution (pH-value, salt


7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


concentration) were adjusted and the organic phase was
added. As a second step, the mixture of both phases was
stirred in a thermostat at 65 C for 45 minutes. During
the mixing, a small amount of the organic component
was dissolved successfully in the aqueous phase due to
the higher solubility at high temperature. The stirrer was
switched of just before the end of the saturation time to
get the two separated phases. After the saturation time,
the vessel contains the mixture was stored in an insu-
lated container to keep it warm. The aqueous phase was
then rapidly cooled down to 25C (the temperature at
which all the measurements were performed) by inject-
ing it into the measuring devices and the excess of the
dissolved organic phase then separated in fine emulsion
droplets. Due to the fast breakdown of the dispersions
and the long measuring time for the zeta potential, it is
important to use stable systems. The size distribution of
the micro droplets as a function of time was measured
using the MICROTRAC UPA 150 Ultrafine Particle An-
alyzer. The zeta potential measurement was more repro-
ducible by this procedure compared to other methods as
mentioned above.


Results

Emulsion Stability:
It was very important to create stable dispersions with
the used EFCE test system which will not separate dur-
ing the zeta potential measurements. The salt-free dis-
persions normally were stable for about 20 minutes in
higher pH-value ranges. The 10 %-value of the cumu-
lative size distribution (Q(1) 10%) of the droplets
slowly increased in micrometer steps within 10 minutes.
For such a system, the 10, 50 and 90 %-value of the cu-
mulative size distribution as a function of time are shown
in Fig. 2. It can be seen that the bigger particles, Q(1)
90 % grow faster than the smaller droplets. The size of
the smallest part of the droplets (Q(1) 10%) kept their
dimension nearly stable until 10 minutes. Compared to
the initial size (xp) of the parts of the distribution at a
time of 5 minutes, the droplets in Q(1) 10% grow
from 0.89 pm to 1.78 pm and the droplets in Q(1)
90 % grow from 1.78 pm to 5.89 pm. One measurement
of the zeta potential takes about 15 minutes. Due to
the small increase in particle size of the droplets within
15 minutes it was assumed that the salt-free dispersions
were stable for a sufficient time to carry out the zeta po-
tential measurements for this kind of systems. Systems
with small amounts of sodium sulfate showed a related
behavior till a concentration of 1 mmol/1. At a concen-
tration of 50 mmol/1 sodium sulfate the dispersions were
not stable long enough to carry out zeta potential mea-
surements. The dispersions separated before the mea-
surements were finished and so no reproducible and re-













-Q(1)-90%
-X .Q(1)=50%
-- Q(1)=10%




---------------------
-. .


0 5 10 15 20 25 30
t/m n

Figure 2: Changes of particle size of different percent-
ages of the cumulative size distribution



liable results were obtained.
Zeta potential:
Due to the limited stability of the dispersions and
the long duration for a zeta potential measurement it
was only possible to determine the zeta potential as a
function of pH-value and salt concentration in a very
small region. Basically it was possible to estimate re-
producible and reliable zeta potential trends only for two
systems. The first system was a pure water/toluene sys-
tem with no sodium sulphate (system A) and the second
system (system B) was a water/toluene system with a
concentration of 1 mmol/1 sodium sulphate. The results
of these measurements can be seen in Fig. 3. As a mat-
ter of principle the zeta potential of the emulsion was
positive at low pH-values and was changing to negative
values at high pH-values. The zeta potential plot showed
a sigmoidal shape in both cases but the maximum values
of the zeta potential were bigger for system A as to give
25 mV at pH-value of 2 and -69 mV at a pH-value of
12. For comparison, the maximum values for system B
were 7 mV at a pH-value of 3 and at 53 mV at a pH-
value of 10. The zeta potential has a value of zero at a
pH-value of about 3.5 for system B and 5.5 for system
A. The intersection of the two curves is at a pH-value of
about 7.5 and at a zeta potential value of about 35 mV.
Especially the measurements between the pH-values be-
tween 7 and 3 were tedious because the dispersion was
often not stable long enough for finishing a scan. As a
consequence, a very large number of repetitive measure-
ments were necessary to get reliable results.
Binary interactions:
The droplet-droplet interaction processes were inves-
tigated with the experimental setup shown above (Fig.
3). The droplet interactions to be seen were on the one
hand the repulsion and on the other hand the coalescence
of the droplets. Special emphasis was placed on ensur-
ing that the droplets were on the same height (residence
time, droplet age) during the interactions and that the


7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


40
Averaged Zeta potential in H20
0 Xaveraged zeta potential in 0 001 mol/ Na2SO4
20
X X

-60
20


















ms 067ms 1 33 ms 2 67ms
% x
x
40ms 20ms ms
0 X X
-60

-80
pH value

Figure 3: Zeta potential as a function of pH-value and
salt concentration of toluene/water at 25







0 ms 0 67 ms 1 33 ms 2 ms 2 67 ms
A Droplet-droplet coalescence of free rising toluene droplets






0 ms 10 ms 20ms 30 ms 40 ms
B Droplet-droplet repulsion of free rising toluene droplets

Figure 4: Comparison of time scales during binary
droplet-droplet interactions events of free ris-
ing toluene droplets in water



droplets were stable (small wobbling was allowed). Ex-
amples of the two main interaction regimes are given
in Fig. 4. Noteworthy are the differences in the time
scale between series A and B. The droplets could stay in
contact for over 40 ms and no coalescence was happen-
ing, resulting in a repulsion event. Compared to this, the
duration of a coalescence event was much shorter and
e.g. the width of the liquid-bridge reached nearly 80 %
of the original droplet diameter within 3 ms. This is a
difference in time scale of one order of magnitude.
Capillary waves:
For a satisfactory numerical simulation of the coales-
cence process it is necessary to take even micro-scale
processes into account. According to this, it was possi-
ble by adjusting the light intensity and the thickness of
the diffuser of the cell to capture and observe the forma-
tion and dispersal of capillary waves which are appear-
ing at the beginning of the coalescence process. The
waves start to form directly at the film rupture and run
along the surface over the whole droplet and are then
reflected back. This can be seen in Fig. 5.
If we take a closer look to the velocity development of







7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


0.333 ms


0.667 ms


-A-1mM Na2S04 saturated
-0- bidistilled water nop-saturated
--bidistilled water saturated

2 4 6 8
pH-value


1.333 ms


Figure 5: Formation and spreading of capillary waves

1.2



0.8
P? I-I *


0 0.5


15 2 2.5
t/ms


Figure 6: Velocity of capillary waves after film rupture


the capillary waves (vcap) in Fig. 6 we can see that the
velocity of the capillary waves, for the coalescence event
shown in Fig. 5, starts with a velocity of 1.1 m/s and is
quickly reduced when the wave is leaving the neck of the
droplets. The velocity is decreasing slower to a value
of about 0.5 m/s when running over the bigger cross-
sections of the droplet at a time of about 3 ms. During
this time, the capillary wave had run over the half of the
droplets surface.
Coalescence probability:
Measurements in three different chemical systems as
a function of the pH-value have been made in order to
estimate the binary coalescence probability of toluene
droplets and a comparison of the results with the zeta po-
tential measurements was made. The coalescence prob-
ability (A(dl,d2)) was calculated as the ratio of coales-
cence events (Ncoa,) in respect to the observed binary
droplet contacts (Nit) following basic approaches from
literature. The coalescence probability is due to this a di-
rect indication for the coalescence tendency of the sys-
tem.


(dld2)


Ncoal


10 12 14


Figure 7: Binary coalescence probability in percent as a
function of pH-value


The results are shown in Fig. 7 for two mutually
saturated and a non-saturated system. As reported e.g.
from Tobin et al. (1990) the coalescence behavior of the
droplets and the coalescence probability was decreasing
at higher pH-values. The maximum of the coalescence
probability was obtained for all systems in a pH-range
from 4.5 to 5.5. As estimated, the binary coalescence
probability of the droplets was higher in the unsaturated
system than in the saturated system. The disturbance of
the film between the droplets, resulting in a reduction
of the resistance for the coalescence can be attributed
to the influence of mass transfer from the droplets to
the aqueous phase. By adding sodium sulfate up to a
concentration of 1 mmol/1 to the aqueous phase, satu-
rated with toluene, the coalescence probability increased
and reached a maximum value of 63% at a pH-value of
5. Consequently, the binary coalescence probability was
higher than in the salt-free systems, in spite of the fact
that both phases were mutually saturated and so mass
transfer is negligible.
In a pH-range from 4.5 to 5.5 we find the maximum
of the binary coalescence probability. Compared to this,
the values of the zeta potential for the different systems
are about zero in a pH-range from 3.5 to 4.5. The abso-
lute value of the zeta potential was getting bigger with
an increasing or decreasing pH-value. The binary coa-
lescence experiments were reflecting this tendency. In
the end, the binary coalescence probability was decreas-
ing for the investigated system and concentration range
with higher zeta potential.


Conclusions

The zeta potential of non-stabilized emulsions a function
of pH-value was studies in ultra-pure systems. Further,
binary droplet interactions of free rising droplets were
investigated and the behavior of capillary waves was
shown. Further, the dependency of binary coalescence











probability as a function of pH-value and the chemical
system was studied.
During the experimental procedure, special attention
was paid on the purity of both the toluene and aqueous
phase. In order to remove any remaining metallic or
ionic contaminants, the organic phase was distilled. For
the aqueous phase, a degassing treatment was necessary
to remove any dissolved gas. To limit the influence of
contaminations, an extensive cleaning procedure for all
parts in contact with organic or aqueous phase was per-
formed.
An adapted temperature-quench method was used for
creating stable toluene/water micro emulsions. The
emulsions were stable long enough for the measure-
ments without using surfactants. It was possible to de-
termine the zeta potential of the emulsions up to a con-
centration of 1 mmol/1 sodium sulphate. Due to the fast
emulsion collapse at higher salt concentration it was not
possible to get reliable results. As to this, faster measur-
ment systems are necessary.
A small-scale experimental setup using a high-speed
camera was developed to investigate the binary droplet
interactions. It was possible to capture the movement of
the droplets over the whole interaction time with high
spatial and temporal resolution. It was possible to ob-
serve the coalescence process in detail by using a macro
lens group.
The zeta potential measurements were compared with
the determined binary coalescence probability of three
different chemical systems as a function of pH-value.
The trend known from literature could be directly con-
firmed by the binary investigations: the higher is the zeta
potential, the lower is the binary coalescence probabil-
ity.

Acknowledgements

The authors are grateful to the German Research Foun-
dation (DFG) for financial support (research project KE
837/11-1 & BA 1569/40-1).

References

Alopaeus, V., Koskinen, J., Keskinen, K. I. and Majan-
der, J., Simulation of the population balances for liquid-
liquid systems in a non-ideal stirred tank. Part 2 param-
eter fitting and the use of the multiblock model for dense
dispersions. Chem. Eng. Sci., 57, 1815-1825 (2002).

BlaB, E., Bildung und Koaleszenz von Blasen und
Tropfen, Chem. Ing. Techn., 60, 935-947 (1988).

Coulaloglou C. and Tavlarides L., Description of Inter-
action Processes an agitated Liquid-Liquid Processes,
Chem. Eng. Sci., 32, 1289-1297 (1977).


7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


Eiswirth, R.T., Bart, H.-J. Experimental Investiga-
tion of Droplet-Droplet-Coalescence in Liquid-Liquid-
Systems. Solvent Extraction: Fundamentals to Industrial
Applications, Vol. II, Bruce A. Moyer, ISBN 1-894475-
81-X, pp. 1231-1236 (2008).

Gabler, A., Wegener, M., Schlauch, S. and Kraume,
M. Transiente TropfengrOBenverteilungen in geriihrten
Fliissig/Fliissig-Dispersionen. Chem. Ing. Techn., 77,
80-84 (2005).

Gomes L., Guimaraes, M., Lopes, J., Madureira, C.,
Stichlmair, J. and Cruz-Pinto, J., Reproducibility of
the Hydrodynamic Performance and Measurements in
a Liquid-Liquid Kiihni Extraction Column-Relevance to
Theoretical Model Evaluation, Ind. Eng. Chem. Res.,
43, 1061-1070 (2004).

Gross-Hardt, E., Henschke, M., Klinger, S. and Pfen-
nig, A., Design of pulsed extraction columns based on
laboratory-scale experiments, International Solvent Ex-
traction Conference ISEC 2002 Proceedings, K.C. Sole,
P.M. Cole, J.S. Preston and D.J. Robinson, The South
African Institute of Mining and Metallurgy, Marshali-
town 2107, South Africa, 1358-1363 (2002).

Henschke, M., Schlieper, L. H. and Pfennig, A., Deter-
mination of a coalescence parameter from batch-settling
experiments, Chem. Eng. J., 85, 369-378 (2002).

Kentish, S., Stevens, G. and Pratt, H., Estimation of Co-
alescence and Breakage Rate Constants within a Kiihni
Column, Ind. Eng. Chem. Res., 37, 1099-1106 (1998).

Klinger, S., Henschke, M. and Pfennig, A., Unter-
suchung von Spaltungs- und Koaleszenzvorgangen in
einer Messzelle mit pulsierten Filllkorpern, Chem. Ing.
Techn., 74, 256-261 (2002).

Kraume, M., Gabler, A. and Schulze, K., Influence of
Physical Properties on Drop Size Distribution of Stirred
Liquid-Liquid Dispersions, Chem. Eng. Techn., 27, 330-
334 (2004).

Marinova, K. G., Alargova, R. G. et al. Charging of Oil-
Water Interfaces due to Spontaneous Adsorption of Hy-
droxyl Ions, Langmuir 12(8): 2045-2051 (1996).

Meyers, D. Surfaces, Interfaces and Colloids, VCH,
Weinheim (1991).

Millies, M. and Mewes, D. Phasengrenzflachen in
Blasenstromungen Teil 3: Koaleszenzhemmung.
Chem. Ing. Techn., 68, 927-933 (1996).

Misek, T., Berger, R., SchrOter, J. Standard test systems
for liquid extraction studies. 2nd Edition: The Institution
of Chemical Engineers, Rugby, UK (1985).







7th International Conference on Multiphase Flow,
ICMF 2010, Tampa, FL, May 30 -June 4, 2010


Oka, K.; Otani, W.; Kameyama, K.; Kidai, M.; Takagi
T. Development of a High-Performance Electrophoretic
Light Scattering Apparatus for Mobility Detection of
Particles with their Stokes'radii of Several Nanometers,
Appl. Theor. Electrophoresis 1, 273-278 (1990).

Pfennig, A. and Schwerin, A., Influence of Electrolytes
on Liquid-Liquid Extraction, Ind. Eng. Chem. Res., 37,
3180-3188 (1998).

Podgorska, W. and Baldyga, J. Scale-up effects on the
drop size distribution of liquid-liquid dispersions in agi-
tated vessels. Chem. Eng. Sci., 56, 741-746 (2001).

Ruiz, M. C. and Padilla, R. Determination of coales-
cence functions in liquid-liquid dispersions. Hydromet-
allurgy, 80, 32-42 (2005).

Ritter, J., Dispergierung und Phasentrennung in
geriihrten Fliissig-Fliissig-Systemen, Dissertation, TU
Berlin (2002).

Rommel, W., Meon, W. and BlaB, E., Hydrodynamic
Modeling of Droplet Coalescence at Liquid-Liquid In-
terfaces, Sep. Sci. Techn., 27, 129-159 (1992).

Simon, M. and Bart, H.-J., Experimental Studies of Coa-
lescence in Liquid/Liquid Systems, Chem. Eng. Techn.,
25, 481-484 (2002).

Sovova, H., Breakage and Coalescence of Drops in a
batch stirred Vessel II. Comparison of Model and Ex-
periments, Chem. Eng. Sci., 36, 1567-1573 (1981).

Ster, O. Elektrochem. 30, 508 (1924).

Tobin, T., Muralidhar, H., Wright, H. and Ramkrishna,
D., Coalescence of charged droplets in agitated liquid-
liquid dispersions. Chem. Eng. Sci., 45, 3491-3501
(1990).

Tobin, T. and Ramkrishna, D., Coalescence of charged
droplets in agitated liquid-liquid dispersions, AIChE J.,
38, 1199-1205 (1992).

Tobin, T. and Ramkrishna, D., Modeling the Effect of
Drop Charge on Coalescence in Turbulent Liquid-Liquid
Dispersions, Canad. J. Chem. Engng., 77, 1090-1104
(1999).

Wright, H. and Ramkrishna, D., Factors affecting coa-
lescence frequency of droplets in a stirred liquid-liquid
dispersion, AIChE J., 40, 767-776 (1994).




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