Segregation of granular material in heaps and silos - discrete to continuum modelling
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Beschreibung
Granular matter is common in many industrial processes as raw materials, intermediate
products or as a final product where usually a high homogeneity is required. However, segregation is a very common phenomenon wherever granular materials are handled and it occurs at different stages.
In order to support the industrial design, it is necessary to understand the mechanisms of segregation and to develop a tool which is able to predict the propensity of segregation depending on product and process properties. The underlying mechanisms of segregation during filling and discharge of silos are discussed in detail. The effects for different configurations of silos (flat bottom vs. inclined hopper; with and without belt conveyor) were investigated using a bimodal mixture of differently sized particles. Moreover, the effect of percolation was studied separately inducing vertical segregation to mixtures composed of particles with different sizes and densities by vibration. On top of that, the effect of gravity in segregation was investigated with help of a silo centrifuge.
A useful tool to support the analysis of segregation processes is the Discrete Element Method (DEM). Calibrated and validated DEM simulations have been used to simulate a pilot scale silo with a belt conveyor at the outlet. On one hand, a standard procedure for the calibration of the required parameters is presented. On the other hand, the influence of some common procedures in DEM, which are used to reduce the computational effort (way of filling, upscaling, periodic boundary conditions), as well as their effect on the measured segregation are described. Finally, a continuum approach is presented which fits the segregation effects using a simplified model to experimental data. This approach is useful to predict the segregation behaviour based on a convective/diffusive model.
Autor*in
Maria del Mar Combarros Garcia
Themen in »Segregation of granular material in heaps and silos - discrete to continuum modelling«
DEM Granular material continuum modeling particle technology segregation segregation silo simolations