GB1015865A - Process and apparatus for specific gravity separation of mixtures of solid particles - Google Patents

Abstract

1,015,865. Hydrocyclones ; washing granular materials. MINISTER OF MINES AND TECHNICAL SURVEYS. Sept. 28, 1962 [Oct. 16, 1961], No. 36953/62. Headings B2H and B2P. Coal or ore pulp containing multi-size particles is cleaned by feeding an unstable aqueous suspension thereof into a hydrocyclone, Fig. 1, in which it passes successively first into a frusto-conical zone 19, Fig. 3, where the particles are stratified forming a gyrating, shifting bed from which coarse particles 22 of low specific gravity are discharged via the central upward current around the air core through a vortex finder 4, secondly into a zone 20 where coarse particles of intermediate specific gravity are separated by centrifugal force into two fractions of which the fraction 24 of lower specific gravity is first discharged from that zone through the vortex finder followed by the fraction 25 of higher specific gravity after it has been recirculated into the zone 19, and finally into a zone 21 where fine particles 23 of low specific gravity are separated and discharged through the vortex finder while the remaining suspension containing particles 26 of higher specific gravity are discharged through the outlet orifice 10. The particles 26 constitute the refuse or the ore concentrate depending on whether coal or ore pulp is being cleaned. The zones 19, 20, 21 are defined by successive frusto-conical surfaces 16, 17, 18 of decreasing included angle forming the lower portion of a vortex chamber 8 into the upper cylindrical portion 8b of which the suspension is fed by a tangential inlet 14. The surfaces 16, 17, 18 may be flat, as shown, or slightly curved to form a continuous convex taper. The vortex finder 4 is adjustable by means of screws 7 in the chamber upper portion 8b above which is provided a discharge chamber 5 having an outlet pipe 15. In Fig. 7 (not shown), a number of hydrocyclones 28, 29, 30 are connected in series, the raw material and water being fed to cyclone 28 at 31, 32. The underflow from cyclones 28, 29 is respectively fed to cyclones 29, 30, while the overflow from the latter are recirculated to the raw feed and that from cyclone 28 is fed to a dewatering device 34 from which clean material is discharged at 35. The overflow from device 34 is recirculated through the cyclones and the refuse is discharged from cyclone 30 at 38. The cyclones are operated under pressure by (a) providing a separate tank and surge tank assembly for each cyclone, or (b) feeding the secondary cyclones 29, 30 by gravity, or (c) introducing compressed air into the vortex of the primary cyclone 28 to maintain an air core therein. Relative dimensions and performance figures are given.