One of aluminium’s advantages over competitor materials is its capacity for repeated recycling with high recovery rates, without loss of quality. Aluminium recycling offers clear energy and environmental benefits; it requires only around five percent of the energy use and emissions associated with primary production. However, the recycling industry faces technical challenges both in making further efficiency improvements to melting and purification systems and in ensuring a steady and reliable scrap stream.
Most new aluminium scrap, also known as pre-consumer scrap, arrives at the recycling industry directly from product manufacturing. The quality and the nature of the alloy is known; in addition, it is often uncoated. This means it can then be melted with little preparation, apart perhaps from baling. Such scrap is usually collected by the re-melters in order to produce new wrought aluminium alloys.
Old aluminium scrap, also called post-consumer scrap, comes into the recycling industry via a very diversified and efficient network of metal merchants and waste management companies equipped with the technology to recover aluminium from vehicles, buildings, household goods, etc. This is often performed with heavy equipment such as shredders in parallel with magnetic separators to remove iron, sink-and-float installations or with eddy current installations to separate aluminium from other materials.
Following collection, sorting and preparation, a portion of this ‘old’ scrap is usually purchased by the refiners and is melted mainly into casting alloys, also known as foundry alloys. Refiners recycle not only scrap from end-of-life aluminium products but also scrap from foundries; turnings, skimmings (dross), etc. A fraction of sorted and prepared scrap is purchased by the aluminium fabrication industry to feed alloy re-melting and casting facilities, ensuring a valuable closed-loop recycling and fabrication process of wrought semi–finished products.
Recyclers use a combination of rotary and reverberatory furnaces that represent about 90% of their furnace technology, while induction technology use is marginal.
The solidification process is closely related to melting and recycling and is also crucial in the aluminium value chain, playing a significant role in the productivity, quality and efficiency of production.