GB485381A - Improvements in and connected with the separation of solid materials of different specific gravities - Google Patents

Abstract

485,381. Separating granular materials. RIDLEY, F. F., and COLLIERY ENGINEERING, Ltd. Nov. 18, 1936, No. 31619. [Class 82 (ii)] Solid materials, particularly raw coal, of different specific gravities and mixed sizes, including fines, are separated by dividing them into predetermined size ranges, the fines being then separated on a pneumatic table and the larger sizes by a heavy liquid process, after which the cleaned products are mixed. Alternatively, the damp materials are divided into two size ranges on a primary screen, the smaller size range including the fines being treated in an upward - current pneumatic deduster, with hot or cold air or gas and fed, minus the dust, to a second screen on which the fines are separated out, after which the fines are treated by a pneumatic stratification process ; the remainder of the material from the second screen is mixed with the larger sizes from the primary screen and the mixture is separated by a wet washing process. In a modification of this method, the pneumatic deduster separates the material into dust, medium fines, and a larger range, the use of a second screen being thereby avoided. In the plant shown, raw coal of sizes ranging, for example, from 100 mm. downwards is fed from a hopper a to a screen c which divides it into two ranges of 100-3 mm. and 3 mm.-0. The larger fraction is passed to a heavy-liquid bath d and the smaller to a pneumatic table e, which may be constructed as described in Specification 457,801. The cleaned coal from the bath d and table e is mixed and fed to a conveyer or bunker, as indicated by the arrows f, and the shale into a container g. The air-borne duct from the table e is taken to a cyclone separator i, the dust from which is mixed with the clean coal from the separators d, e. The heavy liquid adhering to the coal from the bath d is recovered by passing the coal over screens k, k<1>, the latter having a water-jet j above it. The liquid recovered on the screen k is pumped back to the bath d, and the diluted liquid from the screen k<1> to a thickening-tank l. The shale from the bath d is carried to a screen k<2> and the diluted heavy liquid there removed is also returned to the thickener l. The clarified water from the thickener is supplied to the spray j, and the re-concentrated heavy liquid to the bath d. The heavy liquid from the screen k<1> may pass to the thickening-tank by way of a frothflotation plant t, in which any coal particles are removed. The fine coal from the screen c may be passed through a de-duster e<1> which removes the finest dust from it before it passes to the pneumatic table e. If desired, the screen c may be adapted to sub-divide the larger size-range of coal, the different fractions being passed to different heavy-liquid baths or different sections of the same bath.