Newsletter - Aachener Verfahrenstechnik - RWTH Aachen University

Extraction
The research of the extraction group focuses on
the extension of the drop population balance tool
ReDrop. On the basis of lab-scale experiments
with ReDrop, the operating limits and the separation
performance of pilot-plant extraction columns
can be predicted. ReDrop follows a representative
number of drops during their entire
lifetime inside the column. Using Monte-Carlo
methods, phenomena taking place in an extraction
column such as drop sedimentation, breakage,
coalescence and mass transfer are modeled.
Impurities in the liquid-liquid system that
may strongly influence the drop behavior are taken
into account by model parameters that are
fitted to the results obtained from single-drop experiments
with the original liquid-liquid system.
Recent research has focused on the extension
of ReDrop for high viscosity systems. This
research has involved single-drop sedimentation
and mass-transfer experiments with the system
PEG4000 in water (c) + toluene + acetone
(c→d). Then hydrodynamics and separation
performance calculated with ReDrop were
successfully validated with data from pilot-plant
experiments which were performed with a pulsed
sieve-tray extraction column. Further research
focused on the industrial application of Re-
Drop, which was done in cooperation with BASF
SE. On the basis of single-drop experiments with
industrial systems, the separation performance
and operating limits of columns were compared
to pilot-plant experiments. It was shown that Re-
Drop may also be applied to industrial systems
and that, in particular, the operating limits of column
are predicted with high accuracy.
For the reliable application of drop population
balance tools such as ReDrop for extraction columns
with rotating internals, a precise description
of drop residence time in the column is necessary.
Therefore, as part of a project funded by
the German research foundation (DFG), the residence
time of individual drops in the column was
investigated in two single-drop cells with Kühnicompartments.
(see Fig.15).
Thermal Process Engineering
Fig.15: Kühni compartments.
The effect of compartment geometry and operating
conditions such as the counter-current flowrate
and rotor speed on drop residence time have
been investigated systematically. Using experimental
findings, a model is being developed that
is able to describe the residence time of drops in
columns with rotating internals as a function of
the parameters being investigated.
Tailor-Made-Fuel from Biomass
The cluster of excellence “Tailor-Made Fuels
from Biomass” adopts an interdisciplinary approach,
through the application of optimized synthesis
processes of new, biomass-based fuels.
The challenges here are the improvement of the
predictability of the separation of liquid-liquid systems
under the influence of the presence of
bio-based solids and high viscosity of systems.
Such bio-based solids come from the feed biomaterial
as well as from microorganisms from
the fermentation processes and ionic liquids are
used as novel solvents for the dissolution of
biomass in TMFB processes. Thus, to derive a
fundamental understanding of the high viscosity
and the solids on drop sedimentation, mass
transfer and coalescence, which are the essential
steps in liquid-liquid separation. In order to
make a progress in the modelling of the coalescence
an Atomic Force Microscope (AFM) is
used at AVT.TVT, which allows to measure interactions
between two droplets. The attractive
van-der Waals-and repulsive electrostatic forces
between IL-drops ([EMIM][EtSO4]) haven been
The AVT Newsletter Thermal Process Engineering 20