Elsevier

Advanced Powder Technology

Volume 31, Issue 2, February 2020, Pages 843-847
Advanced Powder Technology

Order from Chaos: Dynamics of density segregation in continuously aerated granular systems

https://doi.org/10.1016/j.apt.2019.12.002Get rights and content

Highlights

  • Time dependence of density segregation is quantified with well-mixed particles.

  • Gentle aeration can segregate the components from an initially chaotic mixture.

  • Two dynamic pathways that dominate depending on aeration intensity are identified.

Abstract

Under continual disturbance such as vibration, tumbling, flow or aeration, granular or powder systems can display solid or fluid like behavior. Using a well-mixed system of same size (0.2 mm) non-cohesive glass beads and iron powder, we show that gentle aeration can completely segregate the components thereby reducing the entropy of mixing to create near total order from an initially chaotic mixture. We quantify the time dependence of the segregation process and identify two dynamic pathways that dominate depending on the intensity of the aeration. Such findings can facilitate the search for energy efficient methods to process granular systems in pharmaceutical, mining and waste recovery industries.

Graphical abstract

Snap shots from video recordings of an initially well-mixed 50:50 glass beads (white) and iron powder (black) bed showing how the segregation develops at different superficial velocities, u.

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Section snippets

Acknowledgements

This work was supported in part by JSPS KAKENHI Grant Number JP18H03406 to Jun Oshitani, and the Australian Research Council through a Discovery Project Grant to Derek Y.C. Chan.

References (15)

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  • Conversion air velocity at which reverse density segregation converts to normal density segregation in a vibrated fluidized bed of binary particulate mixtures

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    Citation Excerpt :

    When binary mixtures of different-density particles of the same size are fluidized by airflow through the bottom, normal density segregation occurs; lighter particles move upward and the heavier ones move downward. The fundamentals of the segregation have been widely investigated, and the segregation has been applied to dry gravity separation of particulate mixtures [5–24]. The addition of vibration to the fluidized bed is a useful method to achieve good fluidization of fine cohesive particles [25–32].

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