Three-dimensional simulation of aerosolization of powders when transferring materials in powder form

Almost all industrial sectors are concerned by production or handling of materials in powder form: agri-food, metallurgy, pharmacy, milling, baking, fine chemicals, mining, etc. When such materials in powder form are handled or bagged, a fraction of them is dispersed into the surrounding atmosphere, thereby generating deposition on surfaces and suspension in the air, and potentially leading to risks of occupational exposure to dust or to hazardous substances, and to risks of fire and explosion.

The objective of this study is to develop modelling methods for assessing dust emissions during operations of transferring powders, and for designing collective prevention means suitable for reducing the resulting occupational exposure. The approach adopted will consist in continuing the work done so far through an agreement with the laboratoire Particules, Spray et Combustion (PSC, Particles, Spray and Combustion Laboratory) of the Institut de Mécanique des Fluides de Toulouse (IMFT, Institute of Fluid Mechanics of Toulouse, UMR 5502 CNRS (a joint research unit of the CNRS)). Modelling transfers of powder is currently at a very advanced stage because a simulation tool adapted to suit all of the gas-solid flow regimes encountered in the processes involving powders has been developed. Tt has also been demonstrated that a certain number of physical causes are not responsible for dispersion of the plumes of dust. However, much work remains to be done for the tool to be applicable to the processes.

The main sweep of the planned actions will consist:
- in deepening the modelling of the granular flow in the silo in order to reproduce the phenomena of hysteresis inducing flow irregularities (surges, collapses);
- in systematically studying the sensitivity of the predictions to the computation mesh and, possibly, to the gas turbulence models and to the particle agitation models; and
- in studying the feasibility of prediction by simulation of aerosolization by impact of jets of dust on the floor.

Dissemination will include publications in scientific journals and a thesis manuscript, and, if the results permit, a technology transfer as regards the simulation methods.