Aluminum Details

1. aluminium
SUBMITTED BY –
KRITIKA ARORA
DISHA GULATI
SONAL KATARIA

2. Aluminium is a silver-white metal obtained from bauxite, a
rock composed of more than 50% aluminium hydroxides
formed by weathering in tropical regions. Aluminium is the
earth’s third most abundant element (after oxygen and
silicon) and the most abundant metal in the earth’s crust (8%
by mass). Aluminium bearing compounds have been used
by man from the earliest times. Pottery was made from clays
rich in hydrated silicate of aluminium and at one point in
history aluminium was so valuable that rulers and the
wealthy preferred cutlery made by aluminium instead of
gold. Today more aluminium is produced each year than all
other nonferrous metals combined.
The production of aluminium goes via two different routes:
• primary aluminium production from ore
• recycling aluminium from process scrap and used aluminium
products.

3. The process of producing pure alumina from bauxite (the Bayer Process) has
changed very little since the first plant was opened in 1893. The Bayer process can
be considered in three stages:
Extraction
The aluminium-bearing minerals in bauxite - Gibbsite, Böhmite and Diaspore - are
selectively extracted from the insoluble components (mostly oxides) by dissolving
them in a solution of sodium hydroxide (caustic soda):
Gibbsite: Al(OH)3 + Na+ + OH- ---> Al(OH)4
- + Na+
Böhmite and Diaspore: AlO(OH) + Na+ + OH - + H2O ---> Al(OH)4- + Na+
•Depending on the quality of the ore it may be washed to beneficiate it prior to
processing.
• The ore is crushed and milled to reduce the particle size and make the minerals
more available for extraction.
• It is then combined with the process liquor and sent in a slurry to a heated
pressure digester.
•Conditions within the digester (concentration, temperature and pressure) are set
according to the properties of the bauxite ore.
BAYER’S PROCESS

4. •After the extraction stage the insoluble bauxite residue must be separated from the
Aluminium-containing liquor by a process known as settling.
• The liquor is purified as much as possible through filters before being transferred to
the precipitators.
• The insoluble mud from the first settling stage is thickened and washed to recover
the caustic soda, which is then recycled back into the main process.
Precipitation
Crystalline aluminium trihydroxide (Gibbsite), conveniently named "hydrate", is
then precipitated from the digestion liquor:
Al(OH)4
- + Na+ ---> Al(OH)3 + Na+ + OH-
This is basically the reverse of the extraction process, except that the product's
nature is carefully controlled by plant conditions, including seeding, precipitation
temperature and cooling rate. The "hydrate" crystals are then classified into size
fractions and fed into a rotary or calcination kiln. Undersize particles are fed back
into the precipitation stage.
Calcination
"Hydrate", is calcined to form alumina for the aluminium smelting process. In
the calcination process water is driven off to form alumina:
2Al(OH)3 ---> Al2O3 + 3H2O
The calcination process must be carefully controlled since it dictates the
properties of the final product.

6. Hall-Heroult Process:
In 1886, Charles Hall, an American (23 yrs. old), and Paul Heroult, a
Frenchmen (23 yrs old),
simultaneously and independently developed the process till in use today
to make aluminium metal.
•The purified aluminium oxide is mixed with cryolite, a mixture of sodium fluoride
and aluminium fluoride, and heated to about 980 degrees Celsius to melt the solids.
The mixture melts at a much lower temperature than aluminium oxide would by
itself.
•The hot molten mixture is electrolyzed at a low voltage of 4-5 volts, but a high
current of 50,000-150,000 amps. Aluminum ions are reduced to aluminum metal at
the cathode (the sides and bottom of the electrolysis cell).
• At the anode, oxygen is produced from the oxide ions. The anode material is
carbon in the form of graphite, which also is oxidized and must be replaced quite
frequently
The electricity used to produce aluminum is relatively high. One pound of
aluminum requires 6-8 kilowatts of electrical energy.

8. Background
Physically, chemically and mechanically aluminium is a metal like steel, brass,
copper, zinc, lead or titanium. It can be melted, cast, formed and machined
much like these metals and it conducts electric current. In fact often the same
equipment and fabrication methods are used as for steel.
Light Weight
Aluminium is a very light metal with a specific weight of 2.7 g/cm3, about a third
that of steel. For example, the use of aluminium in vehicles reduces dead-weight
and energy consumption while increasing load capacity. Its strength can be
adapted to the application required by modifying the composition of its alloys.
Corrosion Resistance
Aluminium naturally generates a protective oxide coating and is highly
corrosion resistant. Different types of surface treatment such as anodising,
painting or lacquering can further improve this property. It is particularly useful
for applications where protection and conservation are required.
Electrical and Thermal Conductivity
Aluminium is an excellent heat and electricity conductor and in relation to its
weight is almost twice as good a conductor as copper. This has made aluminium
the most commonly used material in major power transmission lines.
PROPERTIES OF ALUMINIUM

9. Reflectivity
Aluminium is a good reflector of visible light as well as heat, and that together
with its low weight, makes it an ideal material for reflectors in, for example, light
fittings or rescue blankets.
Ductility
Aluminium is ductile and has a low melting point and density. In a molten
condition it can be processed in a number of ways. Its ductility allows products of
aluminium to be basically formed close to the end of the product’s design.
Impermeable and Odourless
Aluminium foil, even when it is rolled to only 0.007 mm thickness, is still
completely impermeable and lets neither light aroma nor taste substances out.
Moreover, the metal itself is non-toxic and releases no aroma or taste substances
which makes it ideal for packaging sensitive products such as food or
pharmaceuticals.
Recyclability
Aluminium is 100 percent recyclable with no downgrading of its qualities. The
re-melting of aluminium requires little energy: only about 5 percent of the
energy required to produce the primary metal initially is needed in the
recycling process.

10. USES
Aluminium Cooking Equipment
Packaging
Used in Aeroplanes.
Aluminium in powerlines.
.
Ideal in construction.

11. Aluminium in building construction
Aluminium is widely used in both
commercial and residential construction -
in such applications as-
 window and door frames
 exterior cladding/siding
 gutters and downspouts
roofing
A potential new application for aluminium is
in the nation's infrastructure, such as bridges
and oil rigs.
In many cases, the low weight, high strength,
and durability of aluminium alloys make
aluminium attractive to construction
contractors.

12. With the likelihood of thousands of concrete and steel-reinforced bridge
decks facing rebuilding due to their age and condition, aluminium could be
a critical alternative building material.
Aluminium is cost-effective because it requires less maintenance and
painting than traditional materials.
It can be installed relatively rapidly and with less inconvenience and
disruption to pedestrian and street traffic.

13. THANK YOU