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Schaefer B.,Institute For Mechanische Verfahrenstechnik | Nirschl H.,Institute For Mechanische Verfahrenstechnik
Chemical Engineering Science | Year: 2010

Fluid flow and charge transport in nanoporous packed beds are closely interrelated due to the formation of the electrochemical double layers on the solid-liquid interfaces, thus giving reason to the term electrohydrodynamic transport. This interrelation results from the formation of electrochemical double layers on the particle surfaces. The electrohydrodynamic transport thus depends on the physicochemical properties of the packed bed, as well as on the on its pore structure, which is also determined by the physicochemical properties. Despite its promising commercial applications, the electrohydrodynamic transport in nanoporous structures is only partly understood. This study presents an empirical model for the hydraulic permeability of packed beds and a capillary model for the interaction of mass and charge transport. The capillary model permits to separate between structural and physicochemical influences, based on experimentally determined parameters. A numerical investigation of the formation and hydraulic permeation of packed beds confirms the empirical model for the hydraulic permeability and gives further insight into the structure of the packed beds. © 2010 Elsevier Ltd.

Schafer B.,Institute For Mechanische Verfahrenstechnik | Schafer B.,Bayer AG | Hecht M.,Institute For Computerphysik | Hecht M.,University of Stuttgart | And 3 more authors.
Journal of Colloid and Interface Science | Year: 2010

Cake filtration is a widely used solid-liquid separation process. However, the high flow resistance of the nanoporous filter cake lowers the efficiency of the process significantly. The structure and thus the permeability of the filter cakes depend on the compressive load acting on the particles, the particles size, and the agglomeration of the particles. The latter is determined by the particle charge and the ionic strength of the suspension, as described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In this paper, we propose a combined stochastic rotation dynamics (SRD) and molecular dynamics (MD) methodology to simulate the cake formation. The simulations give further insight into the dependency of the filter cakes' structure on the agglomeration of the particles, which cannot be accessed experimentally. The permeability, as investigated with lattice Boltzmann (LB) simulations of flow through the discretized cake, depends on the particle size and porosity, and thus on the agglomeration of the particles. Our results agree qualitatively with experimental data obtained from colloidal boehmite suspensions. © 2010 Elsevier Inc.

Geier S.,Institute For Mechanische Verfahrenstechnik | Hernandez-Ortiz J.P.,National University of Colombia | De Pablo J.J.,University of Wisconsin - Madison
Chemie-Ingenieur-Technik | Year: 2011

The translocation of big particles through narrow pores is a very rare event. Therefore, it is not efficient to determine the translocation rate by the means of traditional simulation techniques. In this work, the translocation rate of a spherical particle through a pore was determined using Forward Flux Sampling (FFS). These results were compared to the results obtained by applying traditional simulation techniques. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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