GB415881A - Improvements in or relating to the separation of materials of different specific gravities - Google Patents

Abstract

415,881. Washing granular materials. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Chance, T. ; Merion, Pennsylvania, U.S.A.) July 26, 1933, No. 21052. [Class 82 (ii).] In the sand-flotation process a rotary movement is imparted to the lower portion of the suspension of sand in water and the rotary movement of the upper portion is suppressed so that the lighter material passes across the vessel, either to an overflow or to a discharge aperture below the surface of the suspension, in a substantially rectilinear path. The suppression of the rotary movement in the upper portion of the suspension may be effected either by providing a relatively deep column of suspension above the means which produce the rotation, or by the provision of baffles, or by a combination of these means. In the form shown, the upper portion of the vessel 1 is of rectangular cross-section and the lower portion is conical. An upward current of liquid is introduced at 2, preferably into a column 1<a> containing liquid of lower specific gravity than that of the suspension in the vessel 1, and this liquid is distributed by imparting a rotary movement to the suspension in the conical part of the vessel by means of a rotary agitator 4. A plurality of agitators, or high speed impellers, or tangential liquid jets may be employed to produce the rotary movement and additional liquid for agitating the mass may be introduced through the pipes 7. Baffles 11 are provided to suppress the rotary movement in the upper rectangular portion of the vessel and jets 12 are preferably provided to maintain the fluid properties of the suspension in the corners of the vessel. The material to be separated is fed, with or without water, into a hopper 8, and the discharge into the vessel 1 is controlled by adjustable gates 9, 10, the pressure of the column of material in the hopper 8 being sufficient to force the material under the surface of the suspension. A mixture of the suspension and water is fed by a pipe 6 either to the hopper 8 or to the surface of the suspension in the vessel 1 and carries the light material across the vessel to a discharge overflow 5, the liquid discharged with the light material being returned to the pipe 6. The opening of the hopper 8 and the discharge 5 may extend the full width of the vessel. Jets 13 are provided to maintain the fluid properties of the suspension below the opening from the hopper 8 and the overflow 5. Alternatively, the light material may be allowed to sink as it passes across the bath to a discharge aperture situated below the surface of the suspension. The heavier particles are removed from the lower portion of the vessel, for example by the means described in Specification 396,558.