GB466964A - Process and apparatus for separating solid materials having different specific gravities by means of a suspension - Google Patents

Abstract

466,964. Washing granular materials. NAAMLOOZE VENNOOTSCHAP DOMANIALE MIJN MAATSHCAPPIJ. Jan. 25, 1936, Nos. 2434 and 2435. Convention dates, May 23, 1935 and Nov. 28, 1935. [Class 82 (ii)] In the separation of solid materials, e.g. coal, by gravity separation in a suspension of finely divided solid in liquid the density of the suspension is caused to increase from the top to the bottom of the separating vessel and the floating products and one or more layers of products held in suspension at intermediate levels are removed separately, substantially horizontal currents being created in the suspension to transport the suspended products or both the floating products and the suspended products towards their discharge means. The increase in density may be obtained by allowing the solid constituent of the suspension to sink or by supplying suspensions of different densities at different levels of the tank. The stratification may be controlled by various means, e.g. by the use of currents which are upwardly inclined or by rising currents of air or water. In the form shown in Fig. 1, the horizontal currents are produced by supplying suspension through conduits 23, 24, and 25 which open at different levels in the tank 1. The material to be separated is fed at A and the floating constituents are caught by a rake conveyer 17, drawn up a screen 18, and passed to a screen 19 on which they are sprayed by jets 20. The heaviest constituents sink into a hopper 28 formed by a partition 22 and are removed bv an elevator 2 to a screen 4 on which they are sprayed by jets 5. The intermediates which remain suspended between the top and bottom of the tank are carried across the tank by the horizontal currents and are removed by the conveyer 21 and passed to a screen 14. A plurality of conveyers operating at different levels may be provided. The upper part of the wall of the tank opposite the liquid inlets is made double and the space between the walls leads to a liquid discharge conduit 8. Liquid is also withdrawn by a conduit 10 which collects the overflow from the tank and a conduit 12 which opens into the tank above the space formed by the double walls. The conduits 8, and 12 are provided with control valves 9, 13 respectively, by adjustment of which upwardly inclined currents may be produced in the tank. The liquid withdrawn by the conduits 10, 12 and 8 is returned to the tank after being purified, e.g. by froth flotation, if necessary. The liquids may be mixed or partly mixed before being returned to the conduits 23, 24, 25, in order to maintain the suspension or the liquids may be passed to a common settling tank from which suspension of different densities are withdrawn from different levels and passed to the feed conduits. The liquid draining through the screens 4 and 14 may be purified to separate the slurry from the sand, e.g. by screening, froth flotation, or settling. In the form shown in Fig. 2, each horizontal current is made to sweep a zone of considerable depth, the conduits 23, 24, 25 opening into casing 29, 30, 31 which communicate with the liquid in the tank through slots 33, 34, 35 in a slide valve 32 which is reciprocated up and down. The discharge conduits 8, 12 and 36 also open into chambers 38, 39, 40 communicating with the tank by slots in a slide valve 41. Alternatively, each casing or chamber may be provided with an independent slide valve. The conveyer 17 may be trained round the drum 26 if the material treated is coarse or round the drum 27 if it is fine. A suspension of a mixture of solids in liquid may be used, the solid particles differing in size.or density. A suspension of 25 parts by weight of fluorspar and 25 parts of magnetite in 50 parts of water is referred to.