Analysis of granular material behavior during silo discharging process using ultrafast X-ray CT

Selam Waktola1, 2, Andre Bieberle2, Frank Barthel2, Martina Bieberle2, Uwe Hampel2,3, Krzysztof Grudzień1 and Laurent Babout1

1 Institute of Applied Computer Science, Lodz University of Technology, Lodz, Poland

2 Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, Bautzner Landstr. 400, 01328 Dresden, Germany

3 AREVA Endowed Chair on Imaging Techniques in Energy and Process Engineering, Technische Universität Dresden, 01062 Dresden, Germany

ABSTRACT

In most industrial products granular materials are often required to flow under gravity in various kinds of silo shapes and usually through openings in horizontal bottoms. There are a number of interrelated parameters which affects the flow, such as internal friction, bulk and packing density, hopper geometry, material type and so on. Due to the scanning speed limitation and slightly low resolution of ECT or X-ray CT systems, we were not able to measure the velocity and centrifugal effects of granular materials flow effectively.

The ultrafast electron beam X-ray CT scanner (ROFEX) is a very a high temporal resolution system to investigate structural changes of a granular material during the flow process. Since the images which were scanned using this technology have high temporal resolution to track specified particle movements, it was able to measure the local velocity and investigate the dynamic flow of the material during the discharging process.

This study gives a new insight about the gravitational flow during silo discharging process inside a cylindrical silo model. The granular material is a mixture of Seramis and some doped particles with a previously infiltrated salt, in which they are able to absorb X-ray beams for possibly tracking their velocity and longitudinal / transversal / rotational movements. Additionally, the concentration changes during funnel flow in different scanning height and discharging time is also analysed and described in this paper.

Keywords Dynamic flow effects, gravitational flow, ultrafast X-ray CT.