The Influence of Air Permeation on the Flow Properties of Bulk Solids

• Published in: Chemical engineering & technology 2003-02, Vol.26 (2), p.139-146
• Main Authors: Klein, J., Höhne, D., Husemann, K.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bulk materials; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Granular solids; Material form; Material handling, hoisting. Storage. Packaging; Modeling; Physics; Powders; Rheology; Shear stress; Storage (container, warehouses, silos, etc.)
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.200390020

This paper considers the influence of low air permeation on the flow properties of slightly consolidated bulk solids in steady state flow. A ring shear device was built that enables the powder sample to be permeated during the shear test from below, upwards with flow velocities below the onset of fluidization. Furthermore, a mathematical model predicting the dependence of both the shear stress as well as the location of the shear zone in the shear cell on the aeration degree was developed. This model predicts a reduction of the shear stress with increasing air feed pressure and a sudden displacement of the shear zone from the cover to the bottom of the shear cell for a high degree of aeration. The good agreement between the measured results and the model predictions proves that the influence of the permeation on the flow properties of bulk solids can be traced back to the change of the normal stresses in the shear zone. The influence of low air permeation on the flow properties of slightly consolidated bulk solids in steady state flow is investigated. A ring shear device was built that enables the powder sample to be permeated during the shear test from below, upwards with flow velocities below the onset of fluidization. Furthermore, a mathematical model predicting the dependence of both the shear stress as well as the location of the shear zone in the shear cell on the aeration degree was developed.