Physicochemical influences on electrohydrodynamic transport in compressible packed beds of colloidal boehmite particles

Production and processing of colloidal particles require a deeper understanding of surface charge of particles and interaction of mass and charge transport in packed beds. The assessment of fundamental parameters is rather complex due to the additional influence of the particle charge on the structure of a packed bed. The combination of different measurement techniques (streaming potential and electroosmosis) allows for separating the effects, based on the postulation of a new method to quantify the ratio of surface conductance to liquid conductance. The purpose of this paper is to investigate the influence of the pH value and compression on the electrohydrodynamic transport parameters.Comment: 13 pages including 7 figures, accepted by Journal of Colloid and Interface Scienc

Numerical Investigation of Conductivity Additive Dispersion in High‐Power and High‐Energy NMC‐Based Lithium‐Ion Battery Cathodes: Application‐Based Guidelines

Herein, guidelines are provided for the dispersion of conductivity additive in nickel-manganese-cobalt-oxide-based lithium-ion battery (LIB) cathodes with respect to its influence on electrochemical performance. The contrasting design strategies and operating conditions applicable to high-power and high-energy cathodes lead to significant differences in performance limiting factors for the respective microstructures. Hence, a generalization of the optimum dispersion of the conductivity additive that enhances cell performance in all cases is not possible. In this work, four distinct distributions of conductivity additive agglomerate/aggregate sizes resulting from varying mixing conditions are investigated with respect to their compatibility with cathode microstructures intended for different LIB applications with the help of spatially resolved electrochemical simulations. It is found that in the case of high-power cathodes, wherein ionic transport is the dominant performance limiting factor, a more significant proportion of agglomerates that are bigger in size leads to improved diffusion and intercalation conditions. Conversely, in the case of high-energy electrodes wherein the conductivity additive content is minimized, a larger fraction of smaller aggregates, produced by the fragmentation of the agglomerates during the mixing process are essential to ensure sufficient electrical conductivity

Development of a dynamic process model for the mechanical fluid separation in decanter centrifuges

The flowsheet simulation is a current simulation tool in the areas of research & development, plant design and production of chemical products. The objective of flowsheet simulations is the estimation of the overall process behaviour by solving mass and energy equations. The dynamic flowsheet simulation of particulate processes is a new tool which extends the classical simulation tools which are used in the chemical process engineering by the particle size distribution as one relevant new parameter. The complexity of particulate processes is given by the variety of material properties which depend on the particle size, particle size distribution, the volume fraction of solids and the physicochemical properties. This work illustrates a dynamic process model for continuous centrifuges and considers the material properties of the processed solids and the machine behaviour. First the theoretical framework is presented. Due to the complexity of the material, different material functions, such as the particle size distribution, hindered settling, consolidation or sediment transport used for the dynamic calculation of the process within a lab-decanter centrifuge. Example simulations show the capability of the presented approach. One main feature of the numerical approach is given by the fact, that the small numerical effort reveals the possibility for real time simulations which are applied in the process industry for calculation at the same rate as actual wall clock time