Contact electrification (also called tribocharging) results from the exchange of electrostatic charge during frictional contacts between same-type or different materials. It can be observed in natural phenomena (dust and sand storms, volcanic eruptions) and it is also present in industrial processes dealing with granular material (silo flows, filtration, fluidization) in which it can cause mixing and transport inefficiencies. Furthermore, the accumulation of charge in powder handling processes can also lead to potential hazards, or even spark discharge occurring within silo storage and pneumatic conveying.

Although tribocharging has been known for centuries, the underlying mechanism is not fully understood. The complexity of the system and the number of variables affecting contact electrification makes it challenging to study experimentally. With the help of numerical tools and accurate mathematical models, it is now possible to study and help to predict the evolution of charge in such systems for industrial scale.

In this work, kinetic-theory-based transport models are developed for polydisperse granular and gas-solid flows accounting for contact electrification. The hydrodynamic and the additional charge transport models are assessed through hard-sphere simulation results. The mathematical models are used to study the effect of vessel size on charge build-up in gas-solid suspensions and to model lightning during volcanic eruptions.

Speaker : Lise Ceresiat - postdoc TFL