Compaction of aluminium foil and its effect on oxidation and recycling yield

This is a post-peer-review, pre-copyedit version of an article published in Light Metals 2021, Part of the The Minerals, Metals & Materials Series book series (MMMS). The final authenticated version is available online at: https://doi.org/10.1007/978-3-030-65396-5_96One of the problems when recycling aluminium is its oxidation and consequent metal loss. This is especially critical for the thin sheet/foil materials used for food packaging applications. Compacting the scrap into briquettes may partly reduce such losses in addition to facilitate transport and storage. Shredded aluminium materials of different thicknesses (15-300 microns) were compacted into cylindrical briquettes of 4 cm diameter, each weighting 20 g by uniaxial pressure or moderate-pressuretorsion. A sub-set of briquettes and chips was subsequently oxidized at 650 C, while a sub-set was left untreated. Finally, all samples were re-melted under molten protective salt-flux. Compacting reduced the specific oxidation during the heat-treatment and promoted the coalescence and yield for the heat-treated materials. Both effects were most significant for the thinnest foil in the study (15 microns). The material thickness influenced the porosity and surface roughness of the resultant briquette, as well as the pressure required to reach a given bulk density.acceptedVersio

Characteristic properties and recyclability of the aluminium fraction of MSWI bottom ash

The increasing use of aluminimum in packaging applications results in many different aluminium-based products ending up in consumer mixed-waste bins. This waste is typically incinerated, generating an aluminium-containing bottom ash. The current work investigates the recyclability of the aluminium fraction in the bottom ash from waste incineration plants in the USA, UK and Denmark. Incinerated Al-samples from different size fractions (2–6 mm, 6–12 mm and 12–30 mm) were characterized in terms of inherent oxide thickness, re-melting yield/coagulation and composition. The measured average oxide thickness on Al particles was 68 µm (SD=100), with the metal yield and coagulation efficiency measured to between 76 and 92% and 87–99% respectively. Larger particle size fractions resulted in a higher metal yield due to their higher mass to surface ratio. A simplified model correlating metal yield and particle size was proposed. The aluminium content of the melted material was determined to between 95.6 and 98.5% with main impurities being Fe, Si, Mn, Zn, Mg and Cu, corresponding to major aluminium alloying elements and waste charge components

The Separation Behavior of TiB₂ during Cl₂-Free Degassing Treatment of 5083 Aluminum Melt

Utilizing titanium diboride (TiB2) inoculation for grain-refining purposes is a widely established practice in aluminum casthouses and foundries. Since this inoculation is usually implemented jointly with or between routine melt treatment steps ahead of casting, it is important to know whether and how other melt treatment processes affect the fade of TiB2 particles. For the present study, we investigated the influence of degassing process on the separation behavior of TiB2 particles in aluminum melt. Multiple sampling methods were employed and the samples were analyzed via spectrometer analysis. The removal efficiency of TiB2 during the gas-purging process of 5083 aluminum melt was confirmed to be significant over 10 min of treatment time. The rate at which the TiB2 content decays was found to increase with the impeller rotary speed from 400 rounds per minute (rpm) to 700 rpm. The separation rate of TiB2 particles was obtained to be 0.05–0.08 min−1 by fitting the experimental data. Particle mapping results suggest that the TiB2 particles were separated to a dross layer. The obtained experimental results were used to quantitatively evaluate the conventional deterministic flotation model. The deviation between the conventional model and the experimental data was explained through the entrainment–entrapment (EE) model. Suggestions were made for future analytical and experimental works which may validate the EE model