Dross Formation in Aluminum Melts During the Charging of Beverage Can Scrap Bales with Different Densities Using Various Thermal Pretreatments

Steglich, Jan; Friedrich, Bernd; Rosefort, Marcel

doi:10.1007/s11837-020-04268-4

Cited by 5 publications

(8 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, the results suggest that the uniaxial compaction did not affect the thermal de-coating, while MPT compaction slightly reduced the de-coating efficiency. The fact that the uniaxial compaction, even up to densities of 2 g/cm 3 , does not affect the heat-treatment compared to the loose chips opposes some of Steglich's [10] observations, where bales compacted uniaxially to higher densities (1.11 g/cm 3 ) generated higher dross than those compacted to lower densities (0.69 g/cm 3 ) which was explained by an incomplete de-coating. Crucial differences in re-melting method (submersion in aluminum melt without salt-flux) and material (UBC post-consumer scrap) may cause the deviating observations.…”

Section: Thermal De-coatingmentioning

confidence: 72%

“…According to Wells [9], the heat transferred through bales of UBCs is much lower than through a block of solid aluminum. In a later study, Steglich [10] re-melted UBC bales with different densities, organic content, and pre-treatment conditions. The results indicated that bales compacted more loosely formed less dross during re-melting, for a set-up consisting of a multichamber furnace with molten aluminum heel.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal De-coating Pre-treatment for Loose or Compacted Aluminum Scrap and Consequences for Salt-Flux Recycling

Vallejo-Olivares

Høgåsen

Kvithyld

et al. 2022

J. Sustain. Metall.

View full text Add to dashboard Cite

In aluminum recycling, thermal de-coating pre-treatments remove moisture and organic contamination before re-melting. If the scrap is compacted into bales or briquettes before the thermal treatment and re-melting processes, less surface area is exposed to oxidation in contact with air. However, compaction may also limit the efficiency of the de-coating process. In this study, coated sheets of aluminum were thermally de-coated at varied temperatures and durations. Observations of changes in coating thickness, mass, color, and composition revealed a maximum de-coating efficiency of close to 75% wt due to remaining oxide residues. The relationship between de-coating and compaction was investigated by thermally treating loose shreddings (chips) and briquettes of various densities. The briquettes were compacted by three methods: uniaxial, moderate-pressure torsion (MPT), and MPT at 450 °C (Hot MPT); and the de-coating efficiency was calculated from the mass loss. Subsequently, the samples were re-melted under salt-flux and compared with another set of samples which were re-melted without thermal pre-treatment. The results showed that thermal de-coating significantly promotes the coalescence of loose chips and briquettes compacted uniaxially, up to similar coalescences than initially uncoated aluminum samples. Thermally treating the MPT briquettes, which were more densely compacted, led to less de-coating, and subsequently lower coalescences. The analysis of re-melted material revealed that the coating residues did not significantly affect the composition, while the compaction prevented Mg loss for the uncoated materials. Graphical Abstract

show abstract

Section: Thermal De-coatingmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Thermal De-coating Pre-treatment for Loose or Compacted Aluminum Scrap and Consequences for Salt-Flux Recycling

Vallejo-Olivares

Høgåsen

Kvithyld

et al. 2022

J. Sustain. Metall.

View full text Add to dashboard Cite

show abstract

“…This releases volatile components such as short-chain hydrocarbons. The decomposition leaves a carbon-rich residue, which is gasified in the second stage, provided there is oxygen as a reaction partner in the gas atmosphere [24,25]. To secure a complete removal of the organics during de-coating, the process parameters (temperature, atmosphere, duration) must be carefully controlled.…”

Section: Introductionmentioning

confidence: 99%

Effects of Compaction and Thermal Pre-treatments on Generation of Dross and Off-Gases in Aluminium Recycling

Vallejo-Olivares,

Gertjegerdes,

Høgåsen

et al. 2023

J. Sustain. Metall.

Self Cite

View full text Add to dashboard Cite

Organic coatings are a challenge for aluminium packaging recycling since they tend to increase the re-melting metal losses. A solution is de-coating the scrap via a thermal pre-treatment to burn-off the organics before re-melting. Due to logistic benefits, the scrap is often pressed into bales. This study evaluates the influence of compaction on the de-coating efficiency and off-gas emissions, and its consequences for dross formation and recycling metal yield. Loose chips and two types of briquettes, one loosely compacted by uniaxial pressure and the other compacted by moderated-pressure-torsion to higher densities, were heated to 550 °C while analysing the off-gas emissions using FTIR. The briquettes were subsequently re-melted into a molten heel. Re-melting coated scrap multiplied the % wt of dross by a factor of 2 or 3, depending on the compaction pre-treatment, compared to re-melting uncoated aluminium. The densest briquettes emitted less than half the CO2 and CO gases during de-coating and formed significantly more dross. Compaction to the lower densities showed no tangible effects. The effect of de-coating compacted materials or not was small (± 2% wt dross), which was attributed to carbonaceous residues remaining after the thermal treatment. In conclusion, high compactions by torsion limit the de-coating reactions, which depend on factors such as temperature and gas transport. A complete removal of the organic residues is critical for a more sustainable recycling with less dross generated. Graphical Abstract

show abstract

“…Gökelma [12] assessed the recyclability of used aluminium coffee capsules, one of the packaging examples with higher organics/metal ratio, and obtained higher metal yield and coalescence efficiencies for the capsules that had been thermally pre-treated at 500 °C. The work performed by Steglich [13]- [16] constitutes one of the few research lines that include bale density as a parameter for thermal pre-treatment and remelting. The most recent study [16] covers the recycling of UBC bales with different densities, organic content, and pre-treatment conditions in a multi-chamber furnace process.…”

Section: Introductionmentioning

confidence: 99%

“…The work performed by Steglich [13]- [16] constitutes one of the few research lines that include bale density as a parameter for thermal pre-treatment and remelting. The most recent study [16] covers the recycling of UBC bales with different densities, organic content, and pre-treatment conditions in a multi-chamber furnace process. It showed that lower bale densities promote the removal of organics during heat treatment and that this results in a lower dross formation during re-melting.…”

Section: Introductionmentioning

confidence: 99%

Effect of Compaction and Thermal De-coating Pre-treatments on the Recyclability of Coated and Uncoated Aluminium

et al. 2022

View full text Add to dashboard Cite

Scrap pre-treatments, such as compaction and thermal de-coating, are standard industrial practices for recycling aluminium post-consumer scrap. This study compares the recyclability of a coated and uncoated 8111 alloy under the application of compaction and/or thermal de-coating pre-treatments. Sheets of 600 μm thickness were shredded into chips and compacted by uniaxial pressure, moderate pressure torsion (MPT) or MPT at 450 °C (Hot MPT) into briquettes of 4 cm diameter. A subset of briquettes and loose chips was subsequently heat-treated for 1 hour at 550 °C, while the other set was left untreated. The effectiveness of the heat-treatment for the different compaction methods was examined by mass balance and the internal porosity of the briquettes by computed tomography. Re-melting the samples under molten salt-flux showed that the coalescence of the coated material significantly improves with the thermal de-coating pre-treatment, especially for the loose chips and briquettes compacted uniaxially. Lower coalescences were obtained for the de-coated MPT briquettes, as a result of an incomplete de-coating.

show abstract

Dross Formation in Aluminum Melts During the Charging of Beverage Can Scrap Bales with Different Densities Using Various Thermal Pretreatments

Cited by 5 publications

References 6 publications

Thermal De-coating Pre-treatment for Loose or Compacted Aluminum Scrap and Consequences for Salt-Flux Recycling

Thermal De-coating Pre-treatment for Loose or Compacted Aluminum Scrap and Consequences for Salt-Flux Recycling

Effects of Compaction and Thermal Pre-treatments on Generation of Dross and Off-Gases in Aluminium Recycling

Effect of Compaction and Thermal De-coating Pre-treatments on the Recyclability of Coated and Uncoated Aluminium

Contact Info

Product

Resources

About