Kuliah 8 Aluminium 2012.ppt

8/10/2019 Kuliah 8 Aluminium 2012.ppt

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Aluminium

Kuliah

Metalurgi ekstraktif


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Al di muka bumi


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Sejarah perkembangan Al

In 1807, Sir Humphrey Davy, the

British scientist, postulated the

existence of the element

arguing that alum was the salt

of an unknown metal which he

said should becalled "Alumium".

The name was respelt as the

more euphonious aluminium by

later scientists.


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Awal perkembangan

In 1886, Charles MartinHall and Paul L.T. Hroulteach perfected a similarmethod for producingaluminium lectrolyticallyfrom aluminium oxide

(alumina) dissolved incryolite.

Hall filed patents in theUSA and Hroult inFrance, a fact that was

to have great influenceon the future structureof the industry.


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Perbandingan harga proses

The success of the Hall/Hroultprocess was compounded in 1888when Karl Bayer, an Austrian,developed a viable process forproducing alumina from bauxiteore. While the Deville productioncost savings were the moredramatic in magnitude, the finalfigure (price) was stilluncompetitive with alternativematerials.

The Hall/Hroult invention closedthe critical gap. By 1890 the cost ofaluminium had tumbled some 80percent from Deville's prices (seeFigure 1101.01.04). The metal wasnow a commercial proposition,how would it be used?


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Bauxite di Indonesia

Tembeling, Pulau Bintan, Riau

Tayan, Kalimantan Barat

John Veevaert
http://www.trinityminerals.com/http://www.trinityminerals.com/


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Gibbsite and Boehmite


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Mineral bauxite

Unit Gibbsite Bhmite Diaspore

Composition Al(OH)3 AlO(OH) AlO(OH)

Maximum Alumina

Content% 65.4 85.0 85.0

Crystal System Monoclinic Orthorhombic Orthorhombic

Density gcm-3 2.42 3.01 3.44

Temp. for Rapid

DehydrationC 150 350 450

Bauxite occurs in three main forms depending on both the number of molecules of

water of hydration and the crystalline structure. The three structural forms of bauxite are

Gibbsite, Bhmite and Diaspore.


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Komposisi mineralogi bauxit


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Produksi tahunan Al


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Proses Bayer


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Proses BAyer

Step 1 - Mixing:Crushed and Mixed with CausticSoda, bauxite is pumped into huge digesters.

Step 2 - Digestion:Under high pressure and heat, the

caustic soda dissolves the Alumina, or Aluminum

Oxide, in the bauxite to form Sodium Aluminate.

Step 3 - Clarification:While the Sodium Aluminate

remains in the solution, iron oxides and other solid

impurities drop to the bottom of the settling tank,

where, as red mud, they are pumped to a disposal

pond.

Step 4 - Precipitation:After the Sodium Aluminate is

further cooled, it is agitated and seeded with

Aluminum Hydroxide crystals. These form largercrystals, which gradually settle out of the solution.

Seed crystals and Sodium Aluminate remaining in the

solution are then recirculated.

Step 5 - Calcination:The Aluminum Hydroxide

crystals are roasted at more than 1800 degrees F to

remove the water. A fine white powder, Alumina,

remains half aluminum and half oxygen. It is then

ready for transport to a smelter.


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Proses Bayer

Bauxite, the most important ore of aluminium, contains only 3054% alumina, Al2O3, the rest

being a mixture of silica, various iron oxides, and titanium dioxide.

The alumina must be purified before it can be refined to aluminium metal. In the Bayer

process, bauxite is digested by washing with a hot solution of sodium hydroxide, NaOH, at

175 C. This converts the alumina to aluminium hydroxide, Al(OH)3, which dissolves in the

hydroxide solution according to the chemical equation:

Al2O3+ 2 OH+ 3 H2O 2 *Al(OH)4]

The other components of bauxite do not dissolve. The solution is clarified by filtering off the

solid impurities. The mixture of solid impurities is called red mud, and presents a disposalproblem. Next, the hydroxide solution is cooled, and the dissolved aluminium hydroxide

precipitatesas a white, fluffy solid. Then, when heated to 1050C (calcined), the aluminium

hydroxide decomposes to alumina, giving off water vapor in the process:

2 Al(OH)3 Al2O3+ 3 H2O
http://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Iron_oxidehttp://en.wikipedia.org/wiki/Titanium_dioxidehttp://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Chemical_equationhttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Red_mudhttp://en.wikipedia.org/wiki/Precipitation_%28chemistry%29http://en.wikipedia.org/wiki/Calcinedhttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Calcinedhttp://en.wikipedia.org/wiki/Precipitation_%28chemistry%29http://en.wikipedia.org/wiki/Red_mudhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Hydroxidehttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Aluminahttp://en.wikipedia.org/wiki/Chemical_equationhttp://en.wikipedia.org/wiki/Aluminium_hydroxidehttp://en.wikipedia.org/wiki/Sodium_hydroxidehttp://en.wikipedia.org/wiki/Titanium_dioxidehttp://en.wikipedia.org/wiki/Iron_oxidehttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Aluminium


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Bayer refinery

Kuliah 8 Aluminium 2012.ppt

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