About 390 million tons of bauxite are produced globally every year, 85% of which is used to produce aluminum.
Bauxite is an ore composed of aluminum oxide and other minerals and is the world's main source of aluminum. After mining, bauxite is refined into alumina and then converted into aluminum.
Therefore, aluminum usually goes from ore to metal in three stages.
Phase One: Mining Bauxite
Bauxite is typically mined underground in open-pit mines, with Australia, China and Guinea alone accounting for 72% of global mine production.
Australia is by far the largest bauxite producer and is home to the Weipa mine, the world's largest bauxite mining operation.
Guinea is the third largest bauxite producer, with more than 7 billion tons of bauxite reserves, more than any other country. In addition, Guinea is the world's largest bauxite exporter, with 76% of its bauxite exported to China.
After bauxite is mined from the ground, it is sent to alumina plants around the world to produce alumina, which marks the second stage of the production process.
Phase Two: Alumina Production
In the 1890s, Austrian chemist Carl Josef Bayer invented a revolutionary process for extracting aluminum oxide from bauxite. Today, more than 100 years later, about 90% of alumina plants still use the Bayer process to refine bauxite.
Here are the four key steps of the Bayer process:
High pressure dissolution:
Bauxite is mixed with sodium hydroxide and heated under pressure. During this stage, sodium hydroxide selectively dissolves the aluminum oxide from the bauxite, leaving other minerals as impurities.
filter:
Impurities are separated and filtered from the solution, forming a residue called red mud. After the slurry is discarded, the aluminum oxide is converted into sodium aluminate.
precipitation:
The sodium aluminate solution cools and precipitates into a solid, crystalline form of aluminum hydroxide.
Roasting:
The aluminum hydroxide crystals are washed and heated in a calciner to form pure aluminum oxide-a sandy white material called alumina.
Impurities or red mud left over from the alumina production process is a major environmental concern. In fact, for every ton of alumina produced by an alumina plant, 1.2 tons of red mud are produced, and the amount of red mud currently stored in the world exceeds 3 billion tons.
China is the second largest bauxite producer and largest importer, supplying more than half of the world's alumina.
Several major bauxite-producing countries, including Australia, Brazil and India, are among the largest producers of alumina, but none can match China.
Alumina has applications in a variety of industries, including plastics, cosmetics and chemical production. Of course, much of it is shipped to smelters to produce aluminum.
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Phase Three: Aluminum Production
Aluminum oxide is converted to aluminum by electrolytic reduction. In addition to the alumina itself, another mineral called cryolite and large amounts of electricity are key to the production process. Here is a simple overview of how aluminum smelting works:
In an aluminum smelter, hundreds of electrolytic cells are filled with molten cryolite.
Aluminum oxide (made up of two aluminum atoms and three oxygen atoms) is then added to these electrolytic cells, and a powerful current breaks the chemical bonds between the aluminum and oxygen atoms.
The electrolysis reaction causes pure liquid aluminum to precipitate at the bottom of the electrolytic cell, which is then purified and cast into aluminum products of various shapes and sizes.
China dominates global aluminum production and is the largest consumer. Neighboring India is the second largest producer, with output only one-tenth that of China.