GB449085A - Method of separating materials of different specific gravities - Google Patents

Abstract

449,085. Washing granular materials. CHANCE, H. M., 843, Drexel Building, Philadelphia, U.S.A. Dec. 19, 1934, No. 36358. [Class 82 (ii)] Materials of different specific gravities, e.g. wood chips and gravel, coal and slate, limestone and barytes, &c., are separated by introducing them into a body of separating medium in which the lighter particles will float and the heavier materials will sink, the peripheral layers of the body of medium being maintained in circulation. The lighter particles are carried to a point of discharge by the horizontal flow at the top of the vessel and the heavier particles fall through the substantially stationary central part of the medium and through the reverse stream at the bottom of the vessel to a point of discharge. Any light particles carried down with the heavy particles are picked up by the reverse stream and carried up to join the light particles in the horizontal stream at the top of the vessel. A stream of separating medium is preferably introduced on to the horizontal stream at the top of the vessel, travelling in the same direction as and at a greater velocity than the horizontal stream to carry the light particles rapidly to the discharge. The medium may be water, e.g. for separating wood chips from gravel, a solution, or a suspension of solids, e.g. sand, in a liquid such as water. In the form shown in Fig. 1, the circulation is produced by tangentially disposed jets 4 of water or suspension and the light particles pass over a weir 16 to a dewatering screen 17. The medium drains from the screen into a sump 18 from the lower part of which it is withdrawn by a pump 20 and passed to a box 21 from which it flows on to the top of the circulating medium to assist in carrying the lighter material over to the weir. The heavier particles sink into a classifier column 5 which may be provided with a slide valve 28, Fig. 2, and are removed by means of a refuse chamber 7 controlled by valves 8, 8<1>. The materials may be fed on to the top of the medium through a hopper 13 with an adjustable gate 14, or they may be fed into the central part of the medium by a shoot 29. Instead of discharging the light materials over a weir they may be withdrawn by an elevator, preferably a bucket elevator 24, as shown in Fig. 3, with perforated buckets in which the material is subjected to jets of water from sprays 25. In the form shown in Fig. 2, the circulation is produced by one or more rotating paddle wheels 9, preferably of openwork structure, the paddles 10 being attached to spiders or discs on the shaft 11, the materials being introduced by shoots 29<1> into the paddle wheel. Water or suspension is introduced at 4 when a suspension is used as the separating medium to assist in maintaining the suspension. When a suspension is used a layer of water may be maintained on the top of the medium, as described in Specification 119,038, [Class 82 (ii)].