Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Engineering science >> Mechanics, energetics, process engineering
2 proposition(s).

modeling biomass torrefaction at pilot scale with data measured in laboratory at small scale

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire de Préparation de la Bioressource

01-10-2019

SL-DRT-19-0288

thierry.melkior@cea.fr

Torrefaction is a thermal pretreatment applied to biomass, carried out under neutral atmosphere for several tens of minutes, at temperatures between 200 and 300°C. Once treated, the solid exhibits properties closer to those of coal (fossil), making it suitable to the same industrial facilities as this latter. The biomass platform of CEA Grenoble has been equipped with a pilot-scale torrefaction oven (capacity: 150kg/h of wood). The results obtained in this pilot oven are always out of sync with the torrefaction data measured in the laboratory. Therefore, the validity of the change of scale for this process is questionable. The aim of this thesis is to improve the extrapolation at pilot scale of data measured with small analytical equipment. Three successive phd prepared in the laboratory, have led to a model representing the different chemical transformations of biomass during torrefaction. This model will be used in the proposed phd. This work will require to perform a lot of experimental investigations, in the laboratory (small scale) as well as to participate to torrefaction campaigns with the pilot.

Study of processes involving dense fluid for a circular economy with low environmental impact in the photovoltaic field.

Département des Technologies Solaires (LITEN)

Laboratoire Matériaux et Procédés Silicium

01-10-2019

SL-DRT-19-0594

claire.audoin@cea.fr

The photovoltaic industry (PV) generates a large volume of wastes. In addition to production waste (ingot chunk, kerf-loss powder, silicon scrap, etc.), increasing quantities of end-of-life PV panels will have to be treated by 2030. Considered since 2012 as WEEE waste, it is crucial to develop recycling processes. The processes currently used are essentially mechanical processes that primarily promote the recycling of glass and aluminum frame. The recovery of more critical materials such as silicon, silver, copper ? would give an attractive added values for stakeholder in the recycling field. One of the major barriers in the recovery of these materials is the elimination or the delamination of the encapsulation polymer layer (EVA) to allow full separation of the different layers constituting a PV panels (Glass/EVA/Si-Cells/EVA/Backsheet). To that end, some chemical and thermal processes exist in order to remove the EVA layer. However, these methods remain solutions that are not very respectful of the environment. They produce more or less significant levels of hazardous gaseous or liquid effluents. The challenge is to provide solutions with low environmental impact and economically viable. In this context, two CEA laboratories, the LPSD (DEN) and the LMPS (DRT) have carried out feasibility studies of a treatment process involving one or more non-polluting fluids under subcritical (SubC) or supercritical (SC) like CO2 and water for recycling of PV modules. This method involves little known diffusional and interaction mechanisms with the multilayer structure. The understanding of these mechanisms will eventually define the parameters applicable to the recycling process of PV panels to allow recovery of valuables materials (glass, Si, Ag, for example?.). The aim of the PhD is to explore the potential of processes using supercritical fluids under unconventional conditions for the realization of the different key steps in the treatment of PV panels: delamination and extraction of metals of interest. To understand these mechanisms, the candidate will have the opportunity: to design and make specifics samples, to implement treatments in supercritical and/or subcritical fluids as well as complex systems, to rely on advanced physico-chemical characterizations of surfaces and interfaces.

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