Aluminium is one of the most abundant element on the earth. Due to its low density and resistance to corrosion, it has a lot of applications in various industries. Due to its high strength to weight ratio, the metal is widely used in transportation industry for fabricating bodies of railway coaches. This helps in achieving high fuel efficiency. In construction industry, aluminium is preferred because of its corrosion resistance. Also, aluminium can be given beautiful finishing by bending it into curves which can’t be obtained in case of wood or iron. It is widely used in electronics in wiring and also for making cases and other hardware. It is widely used in packaging of food and beverages.
With such a wide range of usage of the metal, it is obvious that it will eventually produce waste in huge quantities. Aluminium is one of the major waste material in the category of e-waste. The cost of aluminium recycling is far cheaper than the cost of production. The cost of recycling is just 5% of what is required to produce the metal from its ore i.e. bauxite. Hence it is preferred for aluminium to be recycled rather than extracting it from its ore. It is the only material that pays off really well for recycling. Brazil recycles up to 98.2% of the aluminium cans produced.
Recycling of Aluminium
A variety of programs can be implemented to recycle aluminium. Municipal programs are one of the most popular ones for aluminium recycling. In these programs, household items like beverage cans, aluminum foil, aluminum baking trays etc. are recycled.
Around 90 % of the aluminum in building and automotive parts is recycled at the end of use. All of these items can further be sent to aluminum recyclers where the metal is melted down in the secondary production process. Approximately 75% of aluminium produced until now has been recycled and used.
- Aluminium cans and other aluminium waste is first segregated from municipal waste, using an eddy current separator. The waste is further shredded into smaller sized pieces to lessen the volume and make it easier for the machines that separate them.
- To minimize the oxidation losses when the metal melts, waste pieces are then cleaned chemically/mechanically.
- Metal blocks are loaded into the furnace and heated to 650 °C to 850 °C to produce molten aluminium.
- Chlorine and nitrogen gas is used for degassing to remove dissolved hydrogen and dross. Hexachloroethane tablets are used as source of chlorine gas.
- After spectroscopic analysis of the samples, metals like tin, copper, zinc, etc. can be added in appropriate quantities to obtain desired alloys.
- The molten mass can then be cast into desired shapes like rods, slabs, ingots, etc.