GB1382561A - Scrap metal recovery and classification - Google Patents

Abstract

1382561 Sieving apparatus; impact pulverizers; comminuting at low temperatures LINDEMANN MASCHINENFABRIK GmbH 27 April 1973 [27 May 1972] 20196/73 Headings B2A and B2H In a method of recovering metal scrap from articles composed of a number of different metals, e.g. scrap machinery, the articles are broken up into pieces by subjecting them to impact, brittle material which is broken into small pieces by the impact is separated from the larger pieces of less brittle material by causing the smaller pieces to pass through a sieve which retains the larger pieces, and the larger pieces are subjected to further repeated impact and tearing and are then conveyed by centrifugal action away from the sieve. Pieces of scrap to be broken are supplied through a duct 2 to the periphery of a hammer mill, rotor 3 having pivotable hammers 4. The rotor is surrounded by a housing 6 which over a lower portion is constructed as a sector-shaped grating 9 having openings 10 of relatively narrow mesh. A vertical shaft 11 is attached to the housing and has its top end fitted with a grating 12 having openings 13 of larger diameter than the openings 10. The pieces of scrap introduced through the duct 2 are first subjected to impact by the hammers 4. Due to their great brittleness components made of cast rion are broken down easily into small pieces which pass through the grating 9. The other components of the scrap which are less brittle, e.g. those made of copper, aluminium and chromium, are subjected to repeated impact and tearing by the hammers 4. Pieces are eventually formed from these components and are thrown centrifugally upwards by the rotor 3 through the shaft 11. Pieces which can pass through the grating 12 enter a hood 14 and are removed through an outlet 15. Larger pieces fall back on to the rotor to be further reduced by the hammers. High-alloy steel components which cannot be broken up are removed by swinging a pivotable flap 17 inwards to the position shown in chain-dotted lines so as to deflect these components directly into the hood 14. When the scrap contains carbon-steel components the brittleness of the latter may be increased by cooling the scrap. This is done by feeding scrap pieces 27 via a hopper 25 into a receiver 24 where they are compressed into bales 18 between a plunger 26 and a slide 22. After the formation of each bale the slide 22 is raised and the bale is pushed into a chamber 19. When a sufficient number of bales have been pushed into the chamber the slide 22 is lowered and a refrigerant, e.g. liquid nitrogen, is supplied through nozzles 23 to the chamber to cool the bales which are subsequently supplied to the rotor periphery by a plunger 21.