(533b) Demonstration of Scale-out Methodology for Intensified Liquid-Liquid Processes

DEMONSTRATION OF
SCALE-OUT METHODOLOGY FOR INTENSIFIED LIQUID-LIQUID PROCESSES

Eduardo
Garciadiego Ortega, Dimitrios Tsaoulidis, Panagiota Angeli*

University College
London, WC1E 7JE, London, UK

Abstract

Over
the last few years there have been many studies on small scale units aiming at
the intensification of multiphase processes relevant to energy and process
industries. These include (bio)chemical synthesis (i.e. flow chemistry),
absorption, extraction, and (nano)crystallisation. Gas-liquid and liquid-liquid
processes carried out continuously in small channels exhibit fast mixing, high
heat and mass transfer rates, and narrow residence time distributions when
compared to conventional equipment. These advantages, in an industrial context,
would translate to reduced costs, energy savings, diminished waste production,
enhanced safety, and increased product quality.

The
transition of these novel and efficient devices from bench-scale to the
industrial application requires the throughput to increase without losing the
merits of the small scales. The most common strategy to address this is by
reproducing the small scale units in parallel in order to have the required
throughput; this approach is termed scale-out or numbering-up. It contrasts the
traditional scale-up where the size of one unit increases. Flow distributors
are necessary to parallelise a process. Their effectiveness is critical to
bridge the gap between bench and industrial scales for intensified processing.
This challenge is accentuated in multiphase processes where maldistribution in
either the residence time or the phase ratio in the main channels negatively
affects the performance.

In
this work double manifolds are considered for the two-phase flows distribution
(Figure 1). They have several advantages, including, simple arrangement, small
footprint and modularity. To model the flow distribution in the double
manifolds, a new model has been developed following the resistance networks
approach, similar to Al-Rawashdeh’s model [1]. The model can be used to select
the sizes in every section of the double manifold for a given maldistribution
tolerance and required throughput.

Figure 1.
Schematic of a double manifold. Each fluid has a separate inlet; then both
phases are distributed independently and mixed together into the main channels.

We
present a demonstration of a step-by-step methodology to scale-out intensified
liquid-liquid extractions. The process studied is the continuous extraction of
U(VI) from a nitric acid solution into an organic phase using TBP as
extractant. Previous to the scale-out, the single-channel process is
characterised for conditions which result in plug flow. Hydrodynamic
characteristics, such as features of the flow pattern (e.g. plug length and
film thickness) and pressure drop, are related to the mass transfer
performance. The results from the single-channel process are used to design a
double manifold for the numbering-up. The resistance network model is used to
decide the channel sizes in the manifold. Extraction studies are then carried
out in the scale out system.

References

1.    M. Al-Rawashdeh, F.
Yu, T.A. Nijhuis, E. V. Rebrov, V. Hessel, J.C. Schouten, “Numbered-up
gas-liquid micro/milli channels reactor with modular flow distributor,” Chem.
Eng. J. 207–208 (2012) 645–655. doi:10.1016/j.cej.2012.07.028.