Patent GB-547099-A (GB)
Title: Improvements in or relating to the separation of solid materials of different specific gravities
IPC: B03B5/44
Filed: 1940-11-07
Abstract: 547,099. Wet - separating. TROSTLER, F., ANDREWS, T., and HUNTINGTON, HEBERLEIN & CO., Ltd. Nov. 7, 1940, No. 16216. [Class 82 (ii)] In a sink-and-float process for the wet separation of solid materials, the separating medium, in the form of a heavy liquid or solution or a suspension of comminuted solid in a liquid, is fed to the upper part of a body of the medium at one end only where the solid materials are fed thereto and at a distance below the upper surface of the body corresponding substantially to the level at which particles of marginal density would teeter, medium being removed in such a manner as to produce and maintain above the said level and adjacent the discharge zone for the float material a separating zone having substantially no upward current and below that zone a downward current just sufficient to draw downwardly teetering particles which are of marginal density. The rate of removal of the medium is also such as to give the slowest falling materials of these being separated a downward movement approximately equal to or approaching their free falling rate, e.g. 1 mm. per second, and is regulated so as to maintain no more than a slight density differential from the level referred to to the bottom of the medium; the latter has a specific gravity not exceeding .02 more than that of the medium at its point of feed, which is at a depth not greater than one tenth the length of the body from end to end. The medium may be fed to the upper part of the vessel under a small hydrostatic head and the stability of the medium below this level is maintained during separation by regulating the rate of withdrawal so as to establish no more than a slight density differential from that level to the bottom, the specific gravity of the meddum in the lower portion being adjusted continuously by the introduction of liquid of different specific gravity from that fed in at the top. The separating medium is fed continuously into the separating vessel 1 from a small tank 9 through slots 10, 10a, the area of which may be adjusted by a plate and slide member 10b, the rate of admission being regulated by means which adjust the area of cross-section of the pipe through which the medium is supplied at 9a and depending also on the rate of withdrawal over the weir 11. The medium is fed into the portion la of the vessel 1, the sunk material passing into the conical part 1b and then through a passage 3 into a casing 2 whence it is removed by an elevator 4 and discharged at 7. The float material passes along the shallow zone 8a at the top of the vessel and is removed as described in Specification 547,098. In a modification, Fig. 3, the vessel 1 is associated with a retreatment vessel 12 separate from the casing 2 but connected thereto by a duct 13, sunk material being fed to the duct by a conveyer 14. The vessel 12 tapers towards the top so as to facilitate discharge of float material released in this vessel over weirs 11 into launders 15 and so on to' washing screens 16, 17 the medium discharging into a medium screen 18 and thence into a stock tank 19. The density at the zone in which a reseparation of marginal density particles takes place may be altered by decreasing the specific gravity of the medium in the reseparating zone, e.g. by introducing diluted medium from a tank such as 19 into the vessel 1 as at 100. Fig. 2. Specifications 486,771 and 507,661 also are referred to.