Patent GB-1526591-A (GB)
Title: Process for recovering usable materials from waste material containing metals and non-metals
IPC: B03B5/34
Filed: 1976-03-24
Abstract: 1526591 Hydrocarbons; wet separating STAMICARBON BV 24 March 1976 [29 March 1975] 11864/76 Headings B2H and B2P In a process for separating "metals" (which term includes metal from a alloys) particulate non-ferromagnetic metal-containing waste material the particle size of at least a portion of which is in the range of 6 to 50 mm., the waste material is mixed with a liquid separating medium comprising a suspension of fine particles of a weighting material in a liquid and having a specific gravity of at least 2.2, and the mixture is introduced into at least one hydrocyclone having a conical part the apex angle of which is from 45‹ to 90‹, whereby a heavy fraction mainly consisting of suspension and metals having a specific gravity of at least 3 is discharged at the apex of the hydrocyclone and a light fraction mainly consisting of suspension and metals of specific gravity less than 3 is discharged as overflow from the hydrocyclone. The waste material may also contain particles of size less than 6mm and particles of more than 50mm but not exceeding 70mm. The liquid separating medium may consist of a suspension of ferrosilicon or barite in water. The ratio of the internal diameter of a vortex finder of the hydrocyclone to that of the tangential feed pipe thereof is less than 1.5 and the ratio of the internal diameter of the feed pipe to that of a cylindrical part of the hydrocyclone is between 0.22 and 0.28. The diameter of the hydrocyclone cylindrical part need not exceed 600mm. As shown, in a plant for recovering materials from scrap automobiles, a discarded car 1 is flattened between rollers 2 and 3 to a bundle 4 which is ground in a shredder 5. The resulting scrap has ferromagnetic components removed from it by a magnetic separator 7. The remaining non-ferromagnetic metals and plastics are sieved off on a screen 9. The oversize portion is returned to the shredder and the undersize portion is sent to a vessel 11, of the type described in specification 893485, to which waterway may be added at 12 and which feeds a mixture of solids and water at constant pressure to a hydrocyclone 14 which effects a primary separation. The hydrocyclone preferably has a cone-shaped part 16 which may be adjusted axially relative to the cylindrical part 17. A first relatively heavy fraction consisting chiefly of copper and aluminium and their alloys, is discharged at the apex 18 and dewatered on a screen 19. A second relatively light fraction comprising plastics and rubber is discharged through the vortex finder 21, dewatered on a screen 22 discharged at 23. The water from screens 19, 22 is collected in a sump 33 and pumped back to the vessel 11. Part of the recycled water containing fines is passed through a cyclone-thickener 31, the thickened fraction being discharged at 32 and the purified being used again in the plant. The first fraction leaving the screen 19 at 20 is supplied to a vessel 34 where it is mixed with the liquid separating medium and the mixture is fed to a secondary hydrocyclone 36. A heavy fraction of specific gravity greater than 3 and consisting of copper and its alloys is discharged at the apex 37, drained on a screen 38 washed on a screen 39 and discharged at 40. A lighter fraction overflowing at 58 is drained on a screen 41 and together with separating medium from the screens 38, 41 is sent to a supply vessel 42, similar to vessel 11, from which it is fed with separating medium to, at least one tertiary hydrocyclone 43 which has an apex angle of 15‹ to 25‹. A middle fraction, consisting chiefly of aluminium, is discharged at 44 and, after draining and rinsing on screens 46 and 47 is discharged at 48. The lightest fraction, consisting of lighter metals and alloys, is discharged at 45 on to dewatering and rinsing screens 49, 50 and recovered at 51. The liquid separating medium from screens 46 and 49 and the overflow 52 of the vessel 42 is returned to the mixing vessel 34. The purified water from the cyclonethickener 31 is used as spraying water on the rinsing screens 39, 47, 50. Diluted separating medium from the latter is regenerated with two series-connected magnetic separators 56, 57. The regenerated magnetic fraction is passed to the mixing vessel 34 and the water separated off is fed to the sump 33. A supply vessel similar to vessels 11 and 42 may be used for the feed to the hydrocyclone 36. Instead of using rinsing screens, the different fractions may be fed to rotating drum screens submerged in washing liquid.