Aluminium recycling

Aluminum recycling is the process by which aluminum scrap can be reused in products after its initial production. The process involves simply re-melting the metal, which is far less expensive and energy-intensive than creating new aluminum through the electrolysis of aluminum oxide (2 3), which must first be mined from bauxite and refined using the Bayer process. Recycling aluminum scrap requires only 5% of the energy used to make new aluminum from the raw ore. For this reason, approximately 36% of all aluminum produced in the United States comes from old recycled scrap. Used beverage containers are the largest component of aluminum scrap, and most of it is manufactured in aluminum cans.

A common practice since the early 1900s and extensively capitalized during World War II, aluminum recycling is not new. It was, however, a low-profile activity until the late 1960s, when the exploding popularity of aluminum beverage cans finally moved into the public consciousness. Sources for recycled aluminum include aircraft, automobiles, bicycles, boats, computers, cookware, gutters, siding, wire, and many other products that require a strong lightweight material, or a material with high thermal conductivity. As recycling does not matter the element, aluminum can be recycled indefinitely and still be used to produce any aluminum product that could have been used.

The recycling of aluminum has a significant impact on the production of new aluminum, even when the cost of collection, separation and recycling are taken into account. Over the long term, landfills, mines, and international shipping are all considered.

Aluminum recycling uses about 5% of the energy required to create aluminum from bauxite; The amount of energy required to convert aluminum oxide into aluminum can be vividly seen when the process is reversed during the combustion of thermite gold ammonium propellant composite perchlorate. Aluminum die extrusion is a specific way of getting reusable material from aluminum scraps but does not require a large energy output of a melting process. In 2003, half of the aluminum products were sourced from recycled aluminum material.

The benefit with respect to carbon dioxide emissions depends on the type of energy used. Electrolysis can be done using non-fossil fuel sources, such as nuclear, geothermal, hydroelectric, or solar. Aluminum production is attracted to sources of cheap electricity. Canada, Brazil, Norway, and Venezuela have 61 to 99% hydroelectric power and are major aluminum producers. The use of recycled aluminum also decreases the need for mining bauxite. The vast amount of aluminum is used for the purpose of calculating the value of the product. Efficient production and recycling benefits the environment as well.

Aluminum beverage cans are usually recycled by the following method:

The scrap aluminum is separated into a range of categories eg aluminum irony (engine blocks etc.), clean aluminum (alloy wheels). Scraps are classified according to ISRI. Depending on the specification of the required casting ingot, it will depend on the type of scrap used in the start melt. Generally, the scrap is a reverberatory furnace (other methods appear to be less economical and / or dangerous) and melted down to form a “bath”. The molten metal is tested using spectroscopy. After the refinements have been added, the melt can be tested several times to be able to fine-tune the batch to the specific standard. Once the correct “recipe” of metal is available, the furnace is tapped and poured into ingot molds, usually via a casting machine. The melt is then left to cool, stacked and sold on as cast silicon-aluminum ingot to various industries for re-use. Mainly, cast alloys like ADC12, LM2, AlSi132, LM24 etc. are produced. These secondary alloys are used in die cast companies. Nowadays, tilting rotary furnaces are used for aluminum scrap recycling, which gives higher recovery compared to reverberatory furnaces (Skelner Furnace).

Brazil recycles 98.2% of its aluminum can production, equivalent to 14.7 billion beverage cans per year, ranked first in the world, more than Japan’s 82.5% recovery rate. Brazil has topped the aluminum can recycling charts eight years in a row.

White dross, a residue of primary aluminum production and secondary recycling operations, is usually classified as waste, still contains useful quantities of aluminum which can be extracted industrially. The process produces aluminum banknotes, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia) which spontaneously ignites on contact with air; contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, however, the waste has been used as a filler in asphalt and concrete.

* Secondary Aluminum Smelters of the World – A list of companies who produce secondary aluminum (ie, recycled or remelted from scrap metal)