Half a croissant, on a plate, with a sign in front of it saying '50c'
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magnetic separator

separating non-ferrous metal from rubbish
  (+5, -1)
(+5, -1)
  [vote for,

The amount of metal that gets thrown out and ends up in landfill must be huge. There must be a way of separating this metal that is cost comparable to mining. I am currently on holidays in a former tin mining town which has inspired this idea.

My idea is to use a magnetic field to perform the separation. Using a magnet to separate ferrous metal from rubbish is obvious and well known. There is also a method of separating non-ferrous metal using magnets; my idea is a variation on this method.

The already known method of separating non-ferrous metal is to quickly pass (drop) the mix through a gradient magnetic field. The magnetic field produces eddy currents (and hence an opposing magnetic field) in the metal which deflects the metal sideways and thus separated. (sorry, can't provide links; using a rudimentary phone to post this).

This is a pretty good method, but has a few drawbacks. Firstly, the rubbish would need to be an approximately uniform size to be deflected: too big (or small?) and it won't work. Secondly, it only works on a narrow stream of rubbish.

My idea is to *slow* rather than deflect the metal. So drop the rubbish from the top of a tower (evacuated of air) with magnetic field running through it. The non- metal objects reach the bottom before the metal objects. Use a timed capture mechanism to get metal objects.

xaviergisz, Jan 01 2010

(?) Belt-type eddy-current separator http://www.lowcostm...ery.co.uk/metal.asp
Eddies in the spacetime continuum. [MaxwellBuchanan, Jan 01 2010]

US patent 4,070,278 https://patents.goo...om/patent/US4070278
vaguely similar [xaviergisz, Jun 10 2010, last modified Nov 19 2018]


       "to be ..........."   

       to be what ?   

8th of 7, Jan 01 2010

       ah, the internet ate half my idea. I've rewritten the lost bit (its a bit terse; I'm worried it might happen again).
xaviergisz, Jan 01 2010

       The problem would be (if I understand) that it would not be suitable for continuous operation - you need to drop the objects singly or in small batches.   

       Industrial eddy-current belt-type separators seem to handle stuff of a reasonable range of sizes. In any case, you'd probably want to be shredding the input material in order to recover maximum material from mixed-material items, no?   

       But ingenious, so [+]
MaxwellBuchanan, Jan 01 2010

       Yep, the rubbish would be dropped in batches, but this would be frequent (every few seconds).   

       The rubbish could be sorted iteratively: the slow to fall rubbish would be shredded and dropped again.
xaviergisz, Jan 01 2010

       The thing is, modern manufacturing sticks other materials into and on the metals making them harder to get a clean recovery product. The smaller the material is chewed the more likely there will be only metal to put through your non-ferrous spectrometer.
wjt, Jan 01 2010


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