21.4: Recycling Processes and Issues
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After it has been sorted, metal is melted in a furnace that can be of two types. The standard Basic Oxygen Furnace (BOF) and the Electric Arc Furnace (EAF). The latter is the most widely used for recycling. The image below shows the electrodes and roof of a 10 tonne electric arc furnace.
Steel is the most recycled metal, with 400 million tonnes per year being recycled. Most EAF based plants, called mini-mills, refine 50–250 kilotonnes of scrap per year. Some new EAF plants have the capacity to produce up to 1 million tonnes per year .
The electric arc furnace method is explained in detail here. When scrap is recycled, it will contain impurities that have to be removed by blowing oxygen over the molten scrap. Refining is an important step in the EAF steelmaking. Depending upon the specification of the steel made, it is important to remove impurities and alloying elements. EAF is a versatile process and can readily be operated under oxidising or reducing conditions, unlike BOF which is always operated under highly oxidising conditions.