ALUMINIUM PROCESS
ALUMINIUM PROCESS
BAUXITE MINING

Aluminium is the most abundant element in the earth’s crust after oxygen and silicon. Because of its chemical reactivity, aluminium is never found in nature as an element but always in its oxidized form. Other important compounds in the crust, include the hydroxides, a group which includes bauxite, the base raw material for primary aluminium production.

Bauxite is generally extracted by open cast mining from strata, typically some 4-6metres thick under a shallow covering of topsoil and vegetation. Underground bauxite mines are used to exploit pockets or beds of deposit between layers of carbonic rock. In many bauxites, clay is removed by some combination of washing, wet scrubbing and cycloning, even by hand picking or sorting.



ALUMINA REFINING


The aluminium industry relies on the Bayer process (Link: http://www.world-aluminium.org/) to produce alumina from bauxite. It remains the most economic means of obtaining alumina, which in turn is used for the production of aluminium metal – around two tonnes of alumina are required to produce one tonne of aluminium.
Related Link: www.world-aluminium.org/



SMELTING


The production process known as electrolytic reduction, enabling aluminium to become one of the world’s most widely-used metals. The electrolysis takes place in a steel vessel called a cell. The cell, maintained at a temperature of about 965°C, is lined with carbon and contains a melt or electrolyte of molten cryolite. Carbon blocks are suspended above the cell and partially immersed in the electrolyte to act as anodes while the carbon lining of the cell acts as a cathode.

Alumina is fed into the electrolyte and separates into positively charged ions of aluminium and negatively charged ions of oxygen. Direct current applied across each cell moves the ions in opposite directions. The oxygen rises to the anode where it burns the carbon to form carbon dioxide. The molten aluminium settles at the bottom of the cell where, at regular intervals, it is extracted – or tapped – using a vacuum crucible.

To sustain the electrolytic process, alumina is fed into the cells continuously. The raw materials required to produce 1 tonne of aluminium are 1.9 tonnes of alumina; 418kg of carbon (a blend of petroleum coke and pitch) and 17.5kg of aluminium fluoride.

Related Link: www.world-aluminium.org



PROCESSES


Aluminium is such a versatile metal, it can be processed in many different ways depending on the application required. Aluminium can be alloyed with other materials to make an array of metals with different properties. The main alloying ingredients are iron, silicon, zinc, copper, magnesium and manganese.

Related Link: www.world-aluminium.org



Extruding


Aluminium can be extruded to form intricate shapes and sections. It is heated to around 500°C and pushed through a die at great pressure.

Aluminium extrusions are used in commercial and domestic buildings for window and door frame systems, prefabricated houses/building structures, roofing and exterior cladding, curtain walling, shop fronts, etc. Furthermore, extrusions are also used in mass transportation for airframes, road and rail vehicles and in marine applications.
Related Link: http://eaa.net/en/



Forged


Aluminium can be forged by hammering to make stress-bearing parts for aircraft and internal combustion engines.
Related Link: www.aluminium.org/



Cast


Aluminium can be cast into and infinite variety of shapes.
Related Link: www.aluminium.org/

 



Rolled


Aluminium can be rolled into plate, sheets, or wafer thin foils the thickness of human hair. The rolling process changes the characteristics of the metal, making it less brittle and more ductile.

Rolled products are used in home appliances, packaging and transportation, building & construction and many other applications.
Related Link: http://eaa.net/en/



Fine Aluminium products


Aluminium powder, flake and paste can be formed by lowing gas under pressure at molten aluminium. This process forms droplets of different sizes. These aluminium products are used in explosives, rocket fuel, metallurgy, chemicals, inks and decorative materials.
Related Link: www.aluminium.org/



Cables


Aluminium has high electrical conductors, and its light weight and good resistance to corrosion make it ideal for overhead electrical transmissions and distribution cable as well as for power systems and substations.
Related Link: www.aluminium.org/


Gulf Aluminium Council, Dubai, United Arab Emirates. ©2017. All rights reserved. | Disclaimer