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The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite , aluminium 's chief ore, through the Bayer process ) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.
The Hall-Héroult electrolysis process is the major production route for primary aluminium. An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside the shell, cathode blocks are cemented together by ramming ...
Molten cryolite is used as a solvent for aluminium oxide (Al 2 O 3) in the Hall–Héroult process, used in the refining of aluminium. It decreases the melting point of aluminium oxide from 2000–2500 °C to 900–1000 °C, and increases its conductivity [ 16 ] thus making the extraction of aluminium more economical.
The Hall–Heroult method is the primary method of producing modern aluminium and requires high purity alumina to produce aluminium. The Bayer process produces high purity alumina which is then used in the Hall–Heroult process as the main raw material. [9]
The Hall–Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoopes process. This process involves the electrolysis of molten aluminium with a sodium, barium, and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%. [46] [143]
The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer. Bauxite, the most important ore of aluminium , contains only 30–60% aluminium oxide (Al 2 O 3 ), the rest being a mixture of silica , various iron oxides , and titanium dioxide . [ 1 ]
The Cowles process was the immediate predecessor to the Hall-Héroult process—today in nearly universal use more than a century after it was discovered by Charles Martin Hall and Paul Héroult and adapted by others including Carl Josef Bayer. Because of the patent landscape, the Cowles companies found themselves in court.
Charles Martin Hall (December 6, 1863 – December 27, 1914) was an American inventor, businessman, and chemist.He is best known for his invention in 1886 of an inexpensive method for producing aluminum, which became the first metal to attain widespread use since the prehistoric discovery of iron.