Solvent and Reactive Extraction

Solvent extraction is a typical separation step e.g. in downstream processing of fermentation broth, for food and pharmaceutical production, in the mining industry, as well as in general chemical processes.

The scientific focus of our work lies on the drop-based description of the performance of extraction columns with the design tool ReDrop. Also broad expertise has been developed on the selection and optimization of extractants for a given separation task, especially of products from a fermentation broth.

The program ReDrop simulates extraction columns by following an ensemble of individual drops along their trajectory through the column. The basic idea is that the column is properly described, if only the behavior of the underlying mass-transfer elements, namely the drops, is well represented with respect to the few underlying phenomena, namely drop sedimentation, breakage, coalescence, mass transfer, reaction, and axial dispersion. The parameters for the underlying drop models are obtained from standardized laboratory experiments with individual drops of the original material system. In these clearly defined experiments, the specific properties of the real material system are captured, including all disturbing influences of e.g. impurities. Based on these data the behavior of the extraction column can be predicted accurately using suitable models.

In the past, ReDrop has been validated to predict the behavior of industrial extraction systems in a variety of pulsed columns. The accuracy of prediction is better than 10%. As a remarkable success of the drop-based concept, the flooding limit of the column can also be predicted consistently without any specific additional model element – which would conventionally be required. The flooding limit is typically predicted to better than 10% as well.

At PEPs ReDrop is developed further, in order to expand the field of application. One goal is to enable the application of ReDrop for new column geometries, for example by using CFD-simulation results in cooperation with Dominique Toye for estimating the parameters of the implemented models and validation with trajectography. Another field of research is the extension and optimization of drop models, such as sedimentation or breakage and coalescence models. This improves parameter estimation and enlarges the field of application of ReDrop. By implementing new suitable models, it will be possible to simulate systems with high viscosities, which are of specific interest in bio-based chemistry.

Fields of application are e.g. in-situ extraction of functional components from fermentation broth in developing a platform for the conversion of affordable and accessible biobased materials, knowledge-based design of extractors for leaching and phyto-extraction, and extraction and purification of bioactive components with aqueous two-phase systems (ATPS).

A special field of expertise is model-based experimental analysis, which is a special form of optimal design of experiments. In several applications it has been shown that the experimental effort for obtaining parameters from the measurement with a given significance can be reduced by a factor of at least 3 in many cases, if the experimental conditions are chosen optimally.

The development of ReDrop as well as the selection and optimization of extractants is systematically supported by industry in a variety of projects, e.g. with BASF, Bayer Technology Services, Evonik Industries, to name just a few.

Current projects are: 

• Validating mass-transfer models for single drops passing through a concentration gradient in the continuous phase
• Knowledge-based design of solids extraction and leaching applying model-based experimental analysis, accounting for selectivity between components and process costs 
• Extraction and purification of bioactive components with aqueous two-phase systems 
• Recovery of phosphorus from sewage sludge and sewage-sludge incineration ash for recycle to the fields as fertilizer 
• Extraction in systems with increased viscosity and containing fine solids as they are relevant e.g. for biobased feedstock, biochemical downstream processing, and rare-earth element recovery and separation in urban mining

Publications: 

M. Kalem, F. Buchbender, A. Pfennig, 2011: Simulation of hydrodynamics in RDC extraction columns using the simulation tool “ReDrop”.

M.Y. Altunok, M. Kalem, A. Pfennig, 2012: Investigation of Mass Transfer on Single Droplets for the Reactive Extraction of Zinc with D2EHPA.

Buchbender, Onink, Meindersma, de Haan, Pfennig, 2012: Simulation of aromatics extraction with an ionic liquid in a pilot-plant Kühni extractor based on single-drop experiments.

Ayesterán, Kopriwa, Buchbender, Kalem, Pfennig, 2015: ReDrop – A Simulation Tool for the Design of Extraction Columns Based on Single-Drop Experiments.

Kopriwa, Pfennig, 2016: Characterization of Coalescence in Extraction Equipment Based on Lab-Scale Experiments.

Bednarz, Jupke, Spieß, Pfennig, 2019: Aerated extraction columns for in situ separation of bio-based diamines from cell suspensions.

Contact: Andreas Pfennig