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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 ...
Hall–Héroult process – Aluminium oxide (Al 2 O 3) is smelted with coke (C) in a high-temperature electrolysis reaction, yielding the desired pure aluminium (Al) and a mixture of CO and CO 2. Al 2 O 3 (s) + 3 C(s) → 2 Al(s) + 3 CO(g)
In 1891 after Cowles began to advertise "pure aluminum" they were sued by the Pittsburgh Reduction Company. The judge announced his decision in January 1893, finding them to be infringing the patent of Hall and having gained knowledge of his process by hiring away a chemist named Hobbs who was the foreman in Pittsburgh.
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.
Julia Brainerd Hall (November 11, 1859 – September 4, 1926) [1] was the sister of American scientist Charles Martin Hall. She supported him in his discovery of the Hall process for extracting aluminium from its ore. [ 2 ]
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 [ 18 ] thus making the extraction of aluminium more economical.
In general, prehistoric extraction of metals, particularly copper, involved two fundamental stages: first, the smelting of copper ore at temperatures exceeding 700 °C is needed to separate the gangue from the copper; second, melting the copper, which requires temperatures exceeding its melting point of 1080 °C. [10]