Metals are part of our everyday life, used to make cars, trucks, trains, train tracks, ships, aeroplanes, whitegoods, cutlery, pots and pans. Metal is divided into two categories, ferrous and nonferrous. Ferrous metals contain steel and iron, with aluminium, copper and brass, examples of nonferrous metals.
Steel is 100% recyclable and is the most recycled material per tonne in the world. Sorting ferrous metals from nonferrous metals is far easier and less expensive than sorting different plastics due to steels magnetic properties.
The Process of Metal Recycling
The process of metal recycling involves four stages. Metal is collected by scrap yards, where it is sorted into bins. Any nonferrous metal items that have a component of steel or iron is treated as scrap steel. Scrap metal centres then sell the scrap to larger super collectors where it is shredded and then melted in furnaces at high temperatures to produce blocks, ingots or sheets to be sold to manufacturers of metal products.
Below is the metal recycling process in detail:
Collection and sorting
The first step in metal recycling is the collection of all metal products. Adelaide residents bring in a variety of metallic items.
Examples of scrap metal items commonly recycled include whitegoods, radiators, steel or alloy wheels, roller shutters, bicycles and batteries, even the stainless steel kitchen sink can be recycled. Metal items are sorted into rubbish skips, ready to be transported to scrap metal super collectors for processing.
Scrap metal prices are high due to the demand for scrap metal that has been recycled.
Crushing and Shredding
Scrap metal processing plants first crush the metal in compactors so it can be handled on conveyor belts easier. Hammer mills then shred the metal into pieces the size of your hand.
Shredded metal is then placed into magnetic drums that separates ferrous and non ferrous metals. Non metallic materials such as paint or plastic is removed by blowing hot air (550°C) through the shredded metal, sucking up the impurities much like a vacuum.
Melting and Purification
The next step is to melt the different scrap metals in large furnaces. Each metal has a specially designed furnace depending on its properties. The furnaces have fuel-efficient regenerative burners to reduce the amount of energy used and the impact on the environment. They are also equipped with jet stirrers, ensuring an even temperature and composition by promoting metal circulation within the furnaces. The stirring process ensures the highest quality end product.
While in a molten state, the metals are purified further by ‘Eddy current’ electrolysis before being poured into different moulds; depending on the metal, and cooled.
Large aluminium ingots; weighing up to 18 tonne and containing around 1.5 million used cans, are sent to mills where they are rolled into sheets, then bought by aluminium can manufacturers to make into new cans.
Despite the energy costs used in scrap metal recycling, the energy required is less in this case as compared with the making from raw material.
Making steel from recycled cans for example uses 75% less energy than when producing steel from raw materials. Australia has around 90% recycle rate for steel products consumed, with every tonne of recycled steel saving 1130kg of iron ore, over 630kg of coal and 54kg of limestone from being mined.
Benefits of Recycling Scrap Metal
There are many benefits associated with scrap metal recycling. Conserving our natural resources from being mined, reducing greenhouse gasses and water pollution by recycling, reduce landfill dumping of metal that could have been recycled, with the most important benefit is the substantial energy saving that is made from recycling scrap metal compared to manufacturing from raw materials on the environment and our economy.