Aluminiumrecycling

In aluminum recycling the recycling of scrap aluminum ( scrap) is understood as aluminum waste in any form, with " aluminum " is a generic term not only for pure aluminum, but also for the majority occurring alloys.

When aluminum alloys are collected separately and recycled, the corresponding alloys can be recycled from the resulting secondary aluminum without loss of quality. Since the various alloying elements can not be removed during remelting, it comes with not unmixed recording the so-called down-cycling. The great economic and ecological advantage of " recycling aluminum " is that the recycling process compared to the primary production, far less than a tenth of there needed for equivalent amounts of aluminum requires the use of energy.

Method

The for recycling occurring in many places and in many ways and form collected aluminum scrap contains both rolled and cast, next to production wastes which are chips dominate as feinstückiges material, but also metal-rich dross.

The when Umschmelzbetrieb mostly delivered mixed scrap is melted in large volume furnaces ( RDF ) with the addition of about 50 % of a chloride-based salt mixture with an addition of fluorspar (calcium fluoride) at 650-700 ° C under continuous motion of the furnace contents. Here are impurities of the use, principally those of oxide type, recorded in slag flow of the molten salt and also limits further oxidation by the furnace atmosphere. The finished melts are rare cast directly to Rohmasseln; mostly they are placed in a so-called "mixers", will allow for further treatment steps of purification, the structural influence and also the qualification as certain Umschmelzlegierung serve (see melt treatment). The recycled aluminum goes into ingot mold or as process heat preserving liquid metal transport in the further processing, usually to form foundries.

While the actual recycling process, the task of medium Umschmelzbetriebe or even one of the primary smelter is connected remelting, working up the scraps left over from recycling amounts of salt slag falls in a particular branch of waste management.

Mix

• In Germany about 1.3 million tons of aluminum were processed in 2006, of which 0.8 million tons as a casting, which came up 80 % from the recycling.
• Approximately 30 % of the aluminum produced in the U.S. comes from the recycling route.
• Recycling rates worldwide are indicated by 40 % for aluminum.

Economy and ecology

For aluminum, the recycling efficiency is therefore very good because it is much more energy intensive to gain primary aluminum by digestion of bauxite ( aluminum ore ) and its conversion to alumina followed by fused-salt electrolysis to melt as scrap aluminum (melting point> 660 ° C). When aluminum recycling only 5% of the amount of energy of primary production is required. In addition, the amount of residue per ton of aluminum produced reduced from two tonnes of primary aluminum production (especially to landfill render red mud ) to 100 kg for the aluminum recycling (especially recyclable salt slag). For the extraction of aluminum from bauxite electrical energy is required to a significant extent; recycling can also primary energy sources, such as Natural gas can be used.