The electromagnetic metal separator, used in
car scrap yards, may become a very important industrial application of electromagnetic
induction. A car sent for scrapping contains a large amount of metal that may be recycled.
Until recently only the steel could be separated by simply passing the crushed scrap along a
belt over a d.c. electromagnet (see Figure 1(a)).
The ferrous metal was attracted and passed
round under the magnetic roller while the rest of the scrap fell into a hopper. The remainder
of the scrap contained plastic, rubber and a large amount of aluminium and it was this
aluminium that it was desirable to separate.
This further separation can now be
achieved as follows. The remaining scrap is passed along a belt over an a.c. electromagnet
(see Figure 1(b)). This induces eddy currents in the aluminium metal scrap that is then
repelled by the field and flies off sideways while the remaining non-metal scrap continues
along the belt. A very high purity for the aluminium separated by this method has been
claimed. It has also proved extremely effective for separating bottle tops from crushed glass
bottle waste.
Construct a small-scale aluminium metal separator in the laboratory
and test how effective it is.
(A mixture of old milk-bottle tops and small stones is suitable
for the material. A possible laboratory arrangement for this experiment is shown in Figure 1(c).)
