Contact

Dr. Gregory Lecrivain

Head Particle dynamics
g.lecrivainAthzdr.de
Phone: +49 351 260 3768

Experimental investigation of binary granular mixing in a rotating drum using camera and ultrafast X-ray computed tomography

The mixing of two granular species is central to a variety of industrial processes. Notable examples include the mixing of dry granular products in the pharmaceutical, chemical and food processing industry using apparatuses such as mixing drums. Therein, a defined and constant particle concentration within the mixture must be ensured over space and time for high product quality. Differences in particle size, density or shape result in complex segregation dynamics, hindering mixing and increasing energy consumption. The mechanisms associated with particle mixing are generally complex and hard to access with conventional experimental techniques. In the case of a rotating cylindrical drum, in particular, rapid radial segregation and slower axial segregation give rise to three-dimensional segregation.

The aim of this project is the investigation of mixing and segregation dynamics of a two-species granular system with density difference inside such a rotating drum. Of particular interest is the effect of operating parameters, such as drum filling and rotational speed, on the mixing time, with the goal of optimizing the process. Ultrafast X-ray computed tomography is used to obtain high-speed image sequences from cross-sections in the bulk of the drum. Comparison with image sequences from the visible front end of the drum, obtained with a high-speed camera, can reveal differences between front and bulk dynamics. Simulations of the system using the discrete element method are also performed, allowing for a more detailed study of the parameter space. Quantitative information, such as the extent of mixing, is extracted from experimental and simulation data using image processing.

Experimental camera image of the binary granular system in transient state
Figure 1: Experimental camera image of the binary granular system in transient state, from the front plane of the rotating drum (a). X-ray image from the central plane of the drum under the same operating conditions (b). Image from a simulation under the same operating conditions (c)

Funding

This project is funded within the Saxon State Scholarship (Landesstipendium) by the Free State of Saxony.

References

  • Papapetrou, T.N., Lecrivain, G., Bieberle, M., Boudouvis, A., Hampel, U.: An improved contact method for quantifying the mixing of a binary granular mixture. Granul. Matter. 23, 1–13 (2021)
  • Papapetrou, T.N., Lecrivain, G., Bieberle, A., Hampel, U.: Experimental investigation of binary granular mixing in a rotating drum using camera and ultrafast X-ray computed tomography. DECHEMA ProcessNet Fachgruppen MPH & CFD, 09.-10. March 2021, Paderborn, Germany (2021)