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Aluminium smelting
 
 
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Aluminium smelting is the process of extracting aluminium
Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
 from its oxide alumina, generally by the Hall-Héroult process
Hall-Héroult process

The Hall-H?roult process is the major industrial process for the production of aluminium. It involves dissolving alumina in molten cryolite, and electrolysing the solution to obtain pure aluminium metal....
. Alumina is extracted from the ore Bauxite
Bauxite

Bauxite is the most important aluminium ore. It consists largely of the minerals gibbsite Al3, boehmite ?-AlO, and diaspore a-AlO, together with the iron oxides goethite and hematite, the clay mineral kaolinite and small amounts of anatase TiO2....
 by means of the Bayer process
Bayer process

The Bayer process is the principal industrial means of refining bauxite to produce alumina.Bauxite, the most important ore of aluminium, contains only 30-54% alumina, Al2O3, the rest being a mixture of silica, various iron oxides, and titanium dioxide....
 at an alumina refinery.

This is an electrolytic
Electrolysis

In chemistry and manufacturing, electrolysis is a method of separating Chemical bond chemical compound by passing an electric current through them....
 process, so an aluminium smelter
Smelting

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores....
 uses prodigious amounts of electricity; they tend to be located very close to large power stations, often hydro-electric ones, and near ports since almost all of them use imported alumina.

Layout of an aluminium smelter
An aluminium smelter consists of a large number of pots, steel containers lined with carbon, in which the electrolysis takes place; smelting is run as a batch process, with the aluminium metal deposited at the bottom of the pots and periodically drained off.






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Encyclopedia


Aluminium smelting is the process of extracting aluminium
Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
 from its oxide alumina, generally by the Hall-Héroult process
Hall-Héroult process

The Hall-H?roult process is the major industrial process for the production of aluminium. It involves dissolving alumina in molten cryolite, and electrolysing the solution to obtain pure aluminium metal....
. Alumina is extracted from the ore Bauxite
Bauxite

Bauxite is the most important aluminium ore. It consists largely of the minerals gibbsite Al3, boehmite ?-AlO, and diaspore a-AlO, together with the iron oxides goethite and hematite, the clay mineral kaolinite and small amounts of anatase TiO2....
 by means of the Bayer process
Bayer process

The Bayer process is the principal industrial means of refining bauxite to produce alumina.Bauxite, the most important ore of aluminium, contains only 30-54% alumina, Al2O3, the rest being a mixture of silica, various iron oxides, and titanium dioxide....
 at an alumina refinery.

This is an electrolytic
Electrolysis

In chemistry and manufacturing, electrolysis is a method of separating Chemical bond chemical compound by passing an electric current through them....
 process, so an aluminium smelter
Smelting

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores....
 uses prodigious amounts of electricity; they tend to be located very close to large power stations, often hydro-electric ones, and near ports since almost all of them use imported alumina.

Layout of an aluminium smelter


An aluminium smelter consists of a large number of pots, steel containers lined with carbon, in which the electrolysis takes place; smelting is run as a batch process, with the aluminium metal deposited at the bottom of the pots and periodically drained off. Power must be constantly available, since the pots have to be repaired at significant cost if the liquid metal solidifies.

The anode
Anode

An anode is an electrode through which electric charge flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the positive electric current....
s are made of carbon, generally derived from pitch.

A typical smelter contains about 300 pots, each of which produces about a ton of aluminium a day, though the largest proposed smelters are up to five times that capacity.

Environmental issues of aluminium smelters


The process produces a quantity of fluoride
Fluoride

Fluoride is the Redox form of fluorine. Both organic compounds and inorganic compounds containing the chemical element fluorine are considered fluorides....
 waste: perfluorocarbons and hydrogen fluoride
Hydrogen fluoride

Hydrogen fluoride is a chemical compound with the chemical formula HF. It is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers ....
 as gases, and sodium
Sodium fluoride

Sodium fluoride is the chemical compound with the chemical formula NaF. This colourless solid is the main source of the fluoride ion in diverse applications....
 and aluminium fluoride
Aluminium fluoride

Aluminium fluoride is the inorganic compound with the formula aluminiumfluorine3. This colourless solid can be prepared synthetically but also occurs in nature....
s and unused cryolite
Cryolite

Cryolite is an uncommon mineral identified with the once large deposit at Ivittuut on the west coast of Greenland, which ran out in 1987....
 as particulates. This can be as small as 0.5 kg per ton of aluminium in the best plants in 2007, up to 4 kg per ton of aluminium in older designs in 1974. Unless carefully controlled, these fluorides tend to be very toxic to vegetation around the plants.

The Soderburgh process which bakes pitch to form the electrodes produces significant emissions of polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic simple aromatic ring and do not contain heteroatoms or carry substituents....
 as the pitch is baked .

The linings of the pots end up contaminated with cyanide-forming materials; Alcoa
Alcoa

Alcoa, Inc. is the world's third largest producer of aluminum, behind Rio Tinto Alcan and Rusal. From its operational headquarters in Pittsburgh, Pennsylvania, Alcoa conducts operations in 44 countries....
 has a process for converting spent linings into aluminium fluoride for reuse and synthetic sand usable for building purposes and inert waste..

Example aluminium smelters


  • Alcan Lynemouth Aluminium Smelter
    Alcan Lynemouth Aluminium Smelter

    The Alcan Lynemouth Aluminium Smelter is situated on the coast of North East England, south of the village of Lynemouth in Northumberland. The smelter is owned by Canada aluminium company Alcan, who are now officially known as Rio Tinto Alcan....
    , powered by the coal-fired Lynemouth Power Station in north-east England
    England

    native_name =|conventional_long_name = England|common_name = England|image_flag = Flag of England.svg|image_coat = England COA.svg|symbol_type = Royal Coat of Arms...
  • Anglesey Aluminium
    Anglesey Aluminium

    Anglesey Aluminium Metal Ltd. is a joint venture between Rio Tinto Group, Kaiser Aluminium and Chemical Corporation.Its aluminium smelter, located on the outskirts of Holyhead, is one of the largest employers in North Wales, with 540 staff members, and began to produce aluminium in 1971....
    , powered by Wylfa
    Wylfa

    Wylfa is a nuclear power station situated just west of Cemaes Bay on the island of Anglesey, north Wales. Its location on the coast provides an excellent cooling source for its operation....
     nuclear power station in north-west Wales
    Wales

    native_name = Cymru|conventional_long_name = Wales|common_name = Wales|image_flag = Flag of Wales 2.svg|national_motto = ...
  • The Valco aluminium smelter in Ghana
    Ghana

    The Republic of Ghana is a country in West Africa. It borders C?te d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south....
    , powered by the Akosombo Dam
    Akosombo Dam

    The Akosombo Hydroelectric Project , usually referred to as the Akosombo Dam, is a hydroelectric dam in southeastern Ghana. The dam is specifically located at the Akosombo gorge, on the Volta River....
     hydro-electric dam
  • Fjarðaál in Iceland
    Iceland

    Iceland, officially the Republic of Iceland , is an island country located in the North Atlantic Ocean between mainland Europe and Greenland....
    , to be powered by the Kárahnjúkar dam
  • Jharsuguda
    Jharsuguda

    Jharsuguda municipality is the headquarters of Jharsuguda District in the Indian States and territories of India of Orissa....
     in Orissa
    Orissa

    Orissa , is a states and territories of India located on the east coast of India, by the Bay of Bengal. It was established on 1 April 1936 as a province in British India, and consists, predominantly of Oriya language speakers....
    , India
    India

    India, officially the Republic of India , is a country in South Asia. It is the List of countries and outlying territories by total area country by geographical area, the List of countries by population country, and the most populous liberal democracy in the world....
    , to be powered by its own 1215 MW coal-fired power station.
  • Alcoa
    Alcoa World Alumina and Chemicals

    Alcoa World Alumina and Chemicals is a joint venture between Alumina Limited and Alcoa and is abbreviated to AWAC. AWAC's business is the mining of bauxite, the extraction of alumina and the smelting of aluminium....
    's Point Henry smelter
    Point Henry smelter

    The Point Henry aluminium smelting is located near Geelong, Victoria in the suburb of Moolap, Victoria. The smelter has a production capacity of 185,000 tonnes of aluminium a year....
     near Geelong
    Geelong, Victoria

    Geelong is the second largest List of cities in Australia in the States and territories of Australia of Victoria , Australia and is the largest regional centre in the state....
    , Australia
    Australia

    Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
    , powered by its own brown coal fueled power station
    Anglesea Power Station, Victoria (Australia)

    Anglesea Power Station is located at Anglesea, Victoria, in Victoria , Australia. It is coal powered with one steam turbine with a capacity of 150Megawatt of electricity....
     and grid electricity.

See also