The good and bad about recycled aluminum

Aluminum can either be produced from bauxite, as seen in the drawing or from aluminum scrap.

When aluminum is produced from bauxite is it called primary aluminum and from aluminum scrap, secondary aluminum.

Refinement of bauxite is sufficiently expensive and uses a lot of energy so that the secondary aluminum production is important in the global sustainable market. About 40% of aluminum in the US is recovered for secondary refining (US EPA).

The energy used to produce aluminum from aluminum scrap is 5% of the energy used for production of primary aluminum.

At the same time recycled aluminium is in no way inferior to the primary aluminium. The composition of a specific alloy is the same regardless of whether it has been produced from primary aluminium or secondary aluminium or a mixture of both.

The recycling of aluminum processes different forms of aluminum scrap, new scrap and old scrap.

New scrap (or process scrap) is the term used to describe the aluminium scrap produced during the manufacture and fabrication of aluminium alloys until such a time as the products are sold to the end-user.

Old scrap (or used scrap) is recovered from used end-products and aluminium components.

The main environmental issue when recycling of aluminum is the air pollution. When remelting used aluminum scrap a flux layer is necessary to cover the aluminum melt from exposure of the oxygen in the air.

From EPA news, released date 08/04/2009, the Aluminum Recyclers have agreed to implement new environmental improvements and controls. Aleris International Inc., is one of US largest aluminum recyclers, and 13 of its subsidiaries have committed to implementing environmental improvements and controls projected to cost $4.2 million at 15 plants located in 11 states, U.S. Environmental Protection Agency (EPA) and the Justice Department announced today.

From Aleris International Inc. website I found this quote, so did you know that?

Aluminum recycling is easy to do, and it makes a difference to the planet. Recycling a single aluminum can save enough energy to light a light bulb for four hours or to operate a television for three hours.

A lot of the information below is found on Alu-Scout, Aluminium on the net.

The aluminum scrap has to be sorted into type and size using various techniques (magnetic sorting and eddy current sorting, flotation, testing, etc.). Depending on the quality and the amount of impurities in the form of other materials, such as coatings, paint, oil, etc., coatings are subsequently removed from the scrap.

A so-called two-chamber process is used to remelt lacquered scrap. The lacquer is stripped thermally in the first chamber and the scrap then enters the melting furnace. This is not the case with anodized scrap. The aluminum oxide will be found in the dross, which comprises of the cover flux, impurities and metal oxides and can be recovered from this dross afterwards.

Depending on the quality of the molten metal, it may be necessary to carry out an additional step, namely refining. This usually takes place in a holding furnace, in which the melt is cleaned and the desired alloy is achieved by the addition of alloying elements or the removal of impurities.

Most scrap is processed to ingots, which are subsequently processed to produce high-quality aluminum castings. As ever-more sophisticated techniques become available, a larger fraction of the scrap is uniform or well sorted. This makes it possible to produce wrought alloys, extrusion ingots and rolling ingots.

Some people think that secondary aluminum is more difficult to surface finish but this is absolutely not true. The secondary aluminum with a specific composition of the alloy following the specification for the alloy, is as good as primary aluminum for anodizing and other surface finishes.

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