Topic 6.2 - Aluminum

Aluminum

third-most abundant element in the earth’s crust

why is Aluminum preferred?

1. Strong

2. Lightweight

3. Durable

4. Resistant to corrosion

5. Malleable

6. Ductile

7. Odorless

8. Conductive

9. Non-combustible

some uses of Aluminum

• power lines

• electrical equipment

• electronics/appliances

• vehicle/aircraft/spacecraft components

• packaging

• appliances

• buildings/window frames

Bauxite

• primary ore for Aluminum

• most common raw material used to produce alumina )for aluminum metal production)

• composed of various minerals

how to obtain bauxite

through mining

1. prepare mining area

2. bauxite mining

3. crushing

4. ore conveyors

5. rehabilitation

where to find bauxite

mainly tropical and sub-tropical areas

• Africa, West Indies, South America, Australia

effects of bauxite mining to environment

• air pollution from bauxite dust

• aluminum hydroxide

• neurological problems

• titanium oxide

• 1-8% reactive silica

Aluminum hydroxide

could be detrimental to health:

• as pain

• reddening of the nose

• coughing

• pain and redness of the skin

• peeling and itching eyes

Neurological problems

• chronic brain syndrome

• anxiety for no reason

• forgetfulness

• Alzheimer's and Parkinson's disease in adults

Titanium Oxide

effect to those who suffer from eczema skin, heart problems and liver problems

Reactive silica

Exposure to high concentrations can cause:

• shortness of breath

• chest pain

• fatigue

• fainting

• or even death

raw materials in production of Aluminum

• Bauxite

• Caustic Soda (Sodium Hydroxide)

• Cryolite

• Carbon electrodes

• Aluminum fluoride

content of Bauxite

• 45-60% aluminum oxide

• impurities such as sand, iron, and other metals

Caustic Soda

• aka Sodium Hydroxide (NaOH)

• dissolves Aluminum compounds in bauxite

• to separate aluminum from impurities

Cryolite

• aka Sodium Hexafluoroaluminate (Na₃AlF₆)

• used as electrolyte (current conducting medium) for smelting

Carbon Electrodes

• transmit electric current through electrolyte

• as carbon is consumed, it combines with oxygen to form carbon dioxide

Aluminum Fluoride

• AlF₃

• added to lower melting point of electrolyte solution

two processes in the production of aluminum

1. The Bayer Process

2. Hall-Heroult Process

The Bayer Process

refining bauxite ore to obtain Alumina aka Aluminum Oxide (Al₂O₃)

Hall-Heroult Process

smelting the Aluminum Oxide to release pure aluminum (remove oxygen)

Aluminum Transformation

1. Extruding

2. Rolling

3. Casting

Extruding

shaping Aluminum using ready-made or tailored profiles

Rolling

• aluminum is extremely malleable

• can be rolled from 60cm to 2mm

• further processed into foil as thin as 0.006mm

  • still completely impermeable to light, aroma, and taste

Casting

changes properties of aluminum

• adding strength, brilliance, and/or ductility

Why Recycle Aluminum?

i. Environmental

ii. Economic

iii. Community benefits

How many times the same piece of aluminium can be recycled?

According to ”The Aluminium Association”, aluminum drinks cans are the most sustainable form of drinks packaging.

• On average, they contain 73% recycled content, which equates to 20 times more than the recycled content of plastic bottles

How much energy can people save by recycling aluminium?

A 60-watt light bulb can be run for over a day on the amount of energy saved by recycling 1 pound of steel

Recycle Process

1. The Loading Conveyor

2. The Shredder

3. The Magnetic Separator - separate ferrous material from aluminum

4. De-coating

5. Furnace holding furnace (Remelting and casting)

6. Rolling mill

other reasons why Aluminum can/should be recycled

• does not lose its properties when recycled; can be recycled indefinitely

• if recycled, electrolysis isn’t used, which is high in energy consumption

• is easier to remove dyes and other impurities than make new alumina