Unit 6b

Aluminum in the Metal Industry

• Aluminum is the third most abundant element in the Earth's crust.
• It's a valuable metal due to its desirable properties.

Properties of Aluminum

• Strong: Aluminum is a strong metal.
• Lightweight: Aluminum is significantly lighter than other comparable metals.
• Durable: Aluminum withstands wear and tear well.
• Corrosion-resistant: Aluminum's surface forms a protective layer that resists corrosion.
• Malleable: Aluminum can be hammered or pressed into different shapes.
• Ductile: Aluminum can be drawn into thin wires.
• Odorless: Aluminum has no discernible odor.
• Conductive: Aluminum is an excellent conductor of heat and electricity.
• Non-combustible: Aluminum will not spontaneously combust.

Uses of Aluminum

• Power lines
• Electrical equipment
• High-rise buildings
• Window frames
• Consumer electronics
• Household appliances
• Industrial appliances
• Packaging
• Aircraft components
• Spacecraft components
• Ships
• Trains
• Personal vehicles
• Consumer durables (pie chart showing distribution of use)

Raw Materials for Aluminum

• Bauxite: The most common raw material for aluminum production.
• Bauxite is a rock composed of various minerals.
• Bauxite is the primary ore for aluminum.
• Bauxite occurs in tropical and sub-tropical areas like Africa, the West Indies, South America, and Australia.

Bauxite Mining Steps

• Preparation of mining area: Initial steps in bauxite mining
• Bauxite mining: Extraction of the raw material from the ground.
• Crushing: Reduction of the bauxite ore to smaller pieces.
• Ore conveyors: Transportation of the crushed bauxite.
• Rehabilitation: Restoration of the land after mining activities

Effect on the Environment

• Air Pollution: Bauxite dust and aluminum hydroxide can have detrimental health effects, causing pain, reddening of the nose, coughing, and skin irritation.
• Neurological Problems: Exposure to bauxite dust can lead to chronic brain syndrome, anxiety, forgetfulness, and Alzheimer's/Parkinson's disease.
• Health Concerns: Titanium oxide in bauxite is associated with skin irritation and other potential health problems
• Reactive Silica: Containing high concentrations of reactive silica in bauxite can lead to breathing problems, chest pain, fatigue, fainting, and possibly death.

Production of Aluminum (Raw Materials)

• Bauxite: Contains 45-60% aluminum oxide (along with impurities).
• Caustic soda (sodium hydroxide): Used to dissolve aluminum compounds from bauxite, separating them from impurities.
• Cryolite: Electrolyte (current-conducting medium) in smelting; naturally occurring cryolite or synthetically produced.
• Carbon electrodes: Transmit electric current through electrolyte during smelting; carbon is consumed forming carbon dioxide.
• Aluminum fluoride: Added to lower the melting point of the electrolyte.

Production of Aluminum (Processes)

• Bayer process: Refining bauxite ore to obtain aluminum oxide
• Hall-Heroult process: Smelting aluminum oxide to release pure aluminum
  • Alumina (Al₂O₃) + Cryolite (Na₃AlF₆) + Fluorspar (CaF₂) reduced the melting point to 1000°C

Aluminum Transformation

• Extruding: Shaping aluminum using ready-made or tailored profiles.
• Rolling: Extreme malleability allows rolling from large sizes to very thin foils (0.006mm).
• Casting: Changes aluminum properties, adding strength, brilliance, and/or ductility.

Recycling Aluminum

• Recycling aluminum is environmentally and economically beneficial.
• Aluminum cans, in particular, are highly recyclable (73% recycled content, 20 times more than plastic bottles on average).
• Recycling aluminum saves significant energy compared to mining and processing new aluminum.

Recycling Process Steps

• Loading Conveyor: Transport of the recycled aluminum materials.
• Shredder: Reduces scrap metal into small pieces.
• Magnetic Separator: Separates ferrous metals from non-ferrous metals.
• De-coating: Removal of coatings from the scrap material.
• Furnace (Holding Furnace): Remelting the aluminum.
• Rolling Mill: Shaping the remelted aluminum into different products.