In order to be able to recycle scrap metal, it is essential to sort and separate the metals. For this purpose, there are different techniques and methods of metal separation that facilitate the subsequent task of recycling and, subsequently, the recovery of the metal as a material for a new product.
How to sort scrap metal
Separation of non-ferrous metals
In order to know how to separate non-ferrous metals, it is essential to understand how eddy currents work.
How an eddy current separator works
In eddy currents, an eddy current produces the opposite reaction to that generated by a magnet towards a ferrous metal. Instead of attracting, it repels the metal so that it shoots out, separating it from the rest of the flow. This is one of the most commonly used methods for recovering aluminium (a non-ferrous metal).
Physical principle of eddy current metal separation
The physical principle of eddy currents is based on an alternating magnetic field, i.e. a magnetic field where the north and south poles change alternately.
In a magnet, for example, the lines of force generated by the magnetic field are closed from one magnetic pole to the other (North-South). So if you place a ferrous metal inside the lines of force, it will be attracted by the magnet. Conversely, if you place a non-ferrous metal inside the outer lines, they will have no effect on it.
However, if the non-ferrous metal is subjected to an alternating magnetic field, inward currents called eddy currents will be created. These currents generate a magnetic field completely opposite to that of the magnet. This strong opposition of magnetic fields causes a repulsion between them so that the non-ferrous metal will be thrown out of its natural path and separated from the rest of the metals.
Separation of ferrous metals
Ferrous metals are those containing iron. To separate them, the most common alternatives are magnetic and electromagnetic separation.
Both are based on the force of magnetic attraction, but differ in that electromagnetic separation uses electricity and is therefore more powerful. What will determine the use of one or the other will depend on each project, whether it is a permanent magnetic overband, a magnetic roller or an electromagnetic drum.
How magnetic metal separation works
It is based on a magnetic field generated by a set of high-powered magnets. In this way, a ferrous metal that crosses the magnetic field will be attracted to the magnetic block and thus separated from the rest of the materials.
How electromagnetic metal separation works
This method uses electrical excitation energy in a coil wound on a magnetic pole to generate an electromagnetic field.
Thus, when a ferrous material crosses the magnetic field, it will be attracted to the coil and thus separated from other materials.
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