Multidimensional fractionation of finely dispersed particles using cross-flow filtration with superimposed electric field

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The separation of particle fractions with highly specific physical properties from suspensions has a great importance in numerous engineering processes. In many applications, in which finely dispersed multicomponent mixtures of particles with sizes <10 μm and different properties are to be separated in industrially relevant quantities, the fractionation due to only one separation characteristic is no longer sufficient. Within the framework of the DFG Priority Program SPP 2045 " Highly specific and multidimensional fractionation of fine particle systems with technical relevance", a novel cross-flow filtration process with superimposed electrical field was developed in the first funding period. This process represents a method for the highly specific separation of suspensions with the micro and submicron particles (< 10 microns). The fractionation is performed with the help of hydrodynamic and electrophoretic forces. The lift forces and electrophoretic forces cause a pre-classification of the particles in the flow channel in front of the filter area. After that the actual fractionation takes place on the open-pore filter medium by the drag forces acting due to the filtrate rate. The aim of the research project is the further development and the upscaling of the new method, which was studied in the first funding period. The focus of the investigations is on the influence of the process parameters (flow velocity, pressure difference and electric field strength) and the material system (particle shape, composition, additives for potential change) on the hydrodynamic and the electrophoretic equivalent diameter of the fractionation. By means of experimental investigations and supporting simulations of the particle movement in the flow, the particle separation during cross-flow filtration is described in terms of size, shape and electrophoretic mobility and thus the optimal parameter ranges are determined. To obtain additional parameters of the separation process, a multiscale modeling approach is used. On the microscale, the simulations using CFD-DEM coupling are performed, which provide information on the local particle dynamics and hydrodynamics and provide the parameters for the simulation of the overall process on the macro scale. The upscaling of the process has to be performed to provide technically relevant quantities of highly specific ultrafine particle suspensions.