PhD opportunities

Modelling of the Electro-Hydro-Thermo-Mechanical stresses occurring during electrodynamic fragmentation of rocks using High Pulsed Power

Thesis proposal

Area of expertiseGeoscience and Geoengineering
Doctoral SchoolGRNE - Gosciences, Ressources Naturelles et Environnement
SupervisorM. Hedi SELLAMI
Research unitGeosciences
ContactSELLAMI Hedi
Starting dateOctober 1st 2020
KeywordsElectric-Pulse Fragmentation, high pulse power, electrode, rock, dielectric material, modelling
AbstractThe Electric-Pulse Fragmentation (or electrodynamic fragmentation) is a selective comminution method that uses highly energetic electrical pulses applied to a material immersed in a liquid for generating cracks specifically at the boundaries between mineral grains rather than randomly as in a mechanical comminution system. The selectivity arises from differences in electrical and acoustic properties of the components of the material. Its feasibility has been proved for the production of high purity material (silicon) and for waste recycling (valorization of bottom ashes). Compared to the conventional crushing methods, this technique allows improving the liberation of the valuable elements, decreasing the energy consumption of the grinding steps and reducing the production of fine particles which can impede the downstream separation processes. Several studies have recently been performed on this technique, however more work is needed to optimize the competitiveness of this technique and foster its use at an industrial scale. This thesis focuses on the understanding and mathematical modelling of the phenomena involved during this process in order to optimize the operating conditions of its industrial implementation.
The suggested approach for this thesis is divided in three main stages:
- Measurements and analysis of experimental results: This involves analyzing existing results and defining new tests. The objective is to understand, on one hand, the role of the different parameters describing the energy source, the rock and the operating mode on this process and, on the other hand, to formulate the most appropriate hypotheses for a parametric modelling process. This process has to respond to a technical and functional approach. The evaluation of wave/material interactions can be based on different types of characterization, mainly 3D computer tomography.
- Modelling: The work consists in writing equations corresponding to the phenomena involved in the framework of an electro-hydro-thermo-mechanical approach and in identifying the key parameters existing between these different physics. In a macroscopic approach, this theoretical formalism exists, but it needs to be enriched by laws of behavior adapted to these rapid stresses. Two complementary approaches can be envisaged: an approach with equivalent homogeneous medium and another with heterogeneous medium.
- Numerical simulation: Numerical developments and simulations will be carried out in order to analyze the sensitivity of the results to the various factors involved in the electrodynamic fragmentation of rocks.
ProfileMaster degree with excellent level in Mathematics, physics of rocks. Knowledge of material processing, rock mechanics and digital development would be appreciated.
FundingAutre type de financement