Granular mixing and segregation in a horizontal rotating drum: A simulation study on the impact of rotational speed and fill level

Abstract

in Wiley InterScience (www.interscience.wiley.com).The rich phase behavior of granular beds of bidisperse hard spherical particles in a rotating horizontal drum is studied by Discrete Element Method (DEM) simulations. Several flow regimes and various forms of radial segregation, as well as mixing, are observed by systematically varying the operational parameters of the drum, i.e. fill level and angular velocity, over a wide range. Steady states after several dozen revolutions are summarized in two bed behavior diagrams, showing strong correlations between flow regime and segregation pattern. An entropy method quantifies the overall degree of mixing, while density and velocity plots are used to analyze the local properties of the granular bed. The percolation mechanism may provide a qualitative explanation for the distinct segregation processes, and for the transient mixing in nonradially segregated beds. Initially blockwise segregated beds are found to mix before radial segregation sets in. High fill fractions ([65%) show the most intense segregation.

Characterising porosity of multi-component mixtures in rotary mills

“…However, the charge was monosized and the drum had no lifters. Other work, Arntz et al (2008) studied the effect of both filling fractions and mill speed on porosity. However, the particle bed was a binary mixture and the mill had no lifters.…”

“…Most existing models of slurry transport are empirical and assume a uniform porosity (in tumbling mills) of 0.4. This uniformity assumption is inconsistent with evidence from studies of particle packing done in rotating drums (Yang et al, 2003(Yang et al, , 2008Arntz et al, 2008). The models, therefore, are not only difficult to extrapolate beyond experimental conditions, but also inaccurate.…”

“…A significant amount of work has also been done on binary systems (Arntz et al, 2008) for the purpose of studying phenomena such as size segregation and mixing (Baumann et al, 1994;Dury and Ristow, 1999). Some work has also been done on packing density.…”

“…The packing of mixtures has been studied widely (Ouchiyama and Tanaka, 1986;Standish 1987, 1991;Dias et al, 2004;Arntz et al, 2008). From such studies, key concepts can be understood that help in studying multi-component mixtures.…”

“…From such studies, key concepts can be understood that help in studying multi-component mixtures. For rotating drums, in particular, studies have been conducted which investigated porosity and other packing characteristics (Arntz et al, 2008). Some studies have focused on characteristics of multicomponent mixtures such as, mixing and segregation (Hill and Kakalios, 1994;Dury and Ristow, 1999;Ding et al, 2002).…”