Materials Proceedings

The recycling of lithium iron phosphate (LiFePO₄) batteries from electric and hybrid vehicles was investigated, by applying mechanical pretreatment and hydrometallurgical methods. The aim was to extract lithium (Li) into the aqueous solution and precipitate iron (Fe) in the form of ferric iron phosphate (FePO₄). Samples of lithium iron phosphate (LFP) batteries from small electric vehicles provided by the company BEEV were used in this study. Initially, the black mass was isolated using mechanical crushing, screening, and sink–float separation methods, avoiding the need for costly chemical or thermal treatments. The cathodic material was then leached with sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂) to oxidize ferrous to ferric iron, resulting in the precipitation of iron phosphate, which was collected in the solid residue from the leaching process. Leaching tests were conducted by varying the concentrations of sulfuric acid and hydrogen peroxide, as well as the leaching time. It has been indicated that by using a sulfuric acid concentration equal to the stoichiometric requirement, and hydrogen peroxide at four times the stoichiometric amount, Li extraction of greater than 98% was achieved within the first few minutes of leaching, while iron extraction remained below 0.5%.

Geothermal energy is typically produced from underground reservoirs using water as the working fluid to transfer heat energy to surface and eventually to the delivery point. CO₂ has been proposed as an alternative working fluid due to its improved mobility, density and its supercritical phase state, leading thus to so-called CPG (CO₂ Plume Geothermal) systems. As a positive side effect, the injected CO₂ mass circulation in the reservoir can be considered a CO₂ storage mechanism, which, depending on the size of the porous medium, may account for few millions of CO₂ tons. Moreover, the thermosiphon effect, owned to the significant change of fluid density between the injection (cold) and the production wells (hot) as well as to its change along the wells, significantly reduces the need for pumping, hence the operating costs. In this work, we setup a mathematical model that fully describes flow in the production/injection wells doublet as well as in the geothermal reservoir. Subsequently, the model is used to evaluate the sensitivity of the beneficial effects of circulating CO₂ rather than water. Parameters such as reservoir properties, injection temperature and thermal effects, are tweaked to demonstrate the sensitivity of each one to the system performance. The results can be utilized as a guideline to the design of such systems and to the emphasis needed to be paid by the engineers.

A computational fluid dynamics-based study of a corrugated wing section inspired by the dragonfly wing was performed for a low Reynolds number (10’000), focusing on gliding flight. The aerodynamic characteristics are compared to those of a typical technical aerofoil (NACA 0009). The objective of this study is to develop a simulation tool for the design and development of corrugated wings for aerospace applications and to gain a better understanding of the flow over corrugated wing sections. The simulation results were verified using a convergence study and validated by an angle of attack study and comparison with experimental results. The results demonstrated the simulations capability of predicting key flow features but there were some discrepancies from the experimental observations, mainly the prediction of the critical angle of attack. Overall, the simulation results demonstrated a comparable, if not better, aerodynamic performance compared to the technical aerofoil.