Segregation of granular material in heaps and silos - discrete to continuum modelling
Produktform: E-Buch Text Elektronisches Buch in proprietärem
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.weiterlesen
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