Patent GB-1175053-A (GB)
Title: Improvements in the classification of granular materials.
Inventor: LOVEGREEN ALAN TREVOR
IPC: B03B5/72
Filed: 1966-05-11
Abstract: 1,175,053. Wet separation of granular materials. A. T. LOVEGREEN. 9 May, 1967 [11 May, 1966; 3 June, 1966], Nos. 20767/66 and 24740/66. Heading B2H. A mixture of granular materials is classified into heavy and light particles by feeding the mixture into an initially laminar stream of carrier liquid established by projecting the liquid on to a flat, generally horizontal, separating surface so that it flows over the surface at a velocity sufficient to cause migration of the particles to a zone of turbulent breakdown of the laminar flow, or standing wave, so as to set up a ripple of heavy particles at this zone followed by a ripple of light particles, the ripples being subsequently separated. In one embodiment of a continuous machine, Fig. 1, the separating surface is constituted by the upper run 10 of a conveyor belt moving in the direction of the arrow 11 and supported on an air cushion formed by air which is introduced through a header 17 into the interior of a hollow frame 13 from which it escapes, through ports 15 in the frame and ports 16 in a bed-plate 12 carried by the frame, into the space between the bedplate 12 and the underside of the upper run 10. A constant-head water tank 32, having funnels 34 provided with adjustable weirs 35 and discharging in a common overflow pipe 39, is connected to separate flow stabilising tanks 37, 38 by means of outlet pipes 36 having flexible sections 51 which permit fine adjustment of the tanks 37, 38 to be effected transversely of the upper run of the belt by means of screws 47, 48. The tanks 37, 38 contain feed funnels 41, 44 provided with adjustable weirs 42, 45 and with discharge pipes 43, 46 having their orifices lying just above the upper run 10 of the belt. Angularly adjustable segregating nozzles 52, 53 are fed with water through flexible pipes 58. In operation, as shown diagrammatically in Fig. 2, the mixture M of granular materials is fed into the funnel 41 at the same time as water from the motor 37 to form a slurry which, as it discharges from the pipe 43 on to the upper run 10 of the belt, spreads radially outwards, as indicated by the arrows, into a laminar flow. At the zone R, the laminar flow breaks down and a turbulent standing wave pattern is formed. Beyond the zone R, the water continues to spread at a slower and diminishing speed. In the zone R, heavy particles are deposited in a ripple while less dense particles jump over this ripple and are deposited in a similarly contoured ripple beyond. Since the separating surface 10 is moving, these ripples tend to form ribbons stretching parallel to the axis C of the surface. At the same time, the funnel 44 is supplied with water from the tank 38. The water discharging from the pipe 46 on the surface 10 also forms a turbulent zone T whereby further separation of the particles is effected resulting into the formation of ribbons A and B, of heavy and light particles respectively. As the concentrated ribbons of particles move with the belt away from the pipe 46 they encounter the standing wave formations from the nozzles 52 and are separated into a central ribbon A 2  of heavy particles and widely spaced ribbons B 2  of light partides. The least dense particles may be separated from the ribbons B 2 . at this stage. As shown at 53 in Fig. 1, more than one pair of segregating nozzles may be used. Alternatively, or in addition, a second concentrating funnel may be mounted beyond the funnel 44. The light particles are carried over the belt as indicated by the arrows 60a, 61a. Fig. 2, into tailings and middlings troughs 60, 61 mounted on both sides of the belt. The ribbon A 2  may be recycled or passed through another machine. Each discharge pipe 43, 46 may be adjustable in an axial direction and also about the normal to the surface 10. One or both of the channels 41, 44 may be replaced by pipes fed by centrifugal pumps, in which case the tank 32 is dispensed with. In another embodiment of a continuous machine, Fig. 5, the mixture to be separated is fed as a wet or dry ribbon 101 on to a travelling belt 100 along which are arranged primary water jet separation pipes 103-105, secondary jet separation pipes 106, 107, 109, 110 and concentration jet pipes 108, 111. Heavy particles are discharged from the belt 10 as a single ribbon 121c on to a conveyer belt 112 and light particles as two ribbons 122a, 122b on to a conveyer belt 113. A fixed plough may be used in place of the pipes 108, 111 (and 107, 110 if desired) to effect convergence or divergence, as the case may be, of the ripples. A fixed group of tines may also be suspended over the belt 100 for mechanically disturbing any ripple between any pair of separation jets so as to facilitate separation of one type of particles from the other. The belt 100 may be located in a tank and may be submerged for part of its travel where it is subjected to a cross-flow of water for the removal of five contaminants. Fig. 4 shows a batch-type machine the separation surface is made up by the upper surfaces of a vertically displaceable central circular table 70 and of a concentric annylus 71 which normally lie in a common plane. With table 70 in its upper position the mixture is fed as a slurry on its top surface through a pipe 88 and is separated into annular ripples 91, 92 of heavy and light particles respectively. The water and any entrained unwanted particles flow over the outer rim of the annulus 71 into a trough 80 and pass through holes in the bottom thereof into a receptacle 86 whence they are discharged through a drain 87. Control plugs may be inserted in the holes. While the ripple 91 is forming it may be disturbed by a manually or mechanically operated rake 93, 94 travelling in a circular path so as to facilitate separation. When a sufficient quantity of mixture has been separated, the supply of slurry is discontinued and the rake 93, 93 stopped. The table 70 is lowered and a curtain of water is fed through a double-walled skirt 90 depending from a header 89 and impinges on the annulus 71 in the zone between the ripples 91, 92. Part of this water flows outwardly and washes the light particles into the trough 80 and part flows inwardly and carries the heavy particles into a chamber 77. The heavy particles on the table 70 may be displaced into the chamber 77 by water introduced through the pipe 88 or by provision being made for spinning the table. The heavy particles are discharged through a separate outlet 78.