GB2190609A - Minerals separator - Google Patents

Description

GB 2 190 609 A 1 SPECIFICATION vanes in combination are especially

preferred. The tilting of the axis is preferably up to Wto the hori Minerals separator zontal such as 1W- 20' preferably 1/2'- 6'. The vanes would be compatible with collection from both ends This invention relates to a minerals separator. 70 of the cylinder, and might be arranged to rotate with Minerals are conventionally separated on a shak- the cylinder at a rotational speed different from, but ing table. A slurry consisting of powdered minerals within 5% (preferably within 11%) of, the cylinder's in water is supplied as a thin fluid film to part of the speed; the vanes in such aversion maybe replaced top edge of a gently sloping riffled table, which is by equivalent means, such as jets or curtains of shaken (with asymmetric acceleration) parallel to the 75 liquid.

top edge. Simultaneously, a film of washing water is If the cylinder is tapered, the half-angle of the applied to the rest of the top edge. The denser part- frustum is preferably up to 450, such as 1/2'to 1We.g.

icles in the film move downhill more slowly than the 1/2'to 20. The speed of rotation of the frustum or lighter particles, but are shaken sideways fasterthan other cylinder is preferably such as to generate a cen- the I ighter particles, and hence maybe collected sep- 80 trifugal force of from 5g to 5009, and it wil I be app arately. reciated that with such centrifugal force, the rotation According to the present invention, a minerals axis can be vertical, horizontal or at any angle, with separator comprises a body having a surface having (at any non-vertical angle) a useful contribution from the form of the inside of a cylinder (which may be Earth's gravity in cyclically perturbing particles held tapered) arranged when rotating about its axisto 85 centrifugally.

have a force acting axially along it, means for rotat- In all cases, washing liquid is preferably applied ing the bodyaboutthe axis of the cylinderto apply a intermittently or more preferably continuouslytothe centrifugal force exceeding g to said surface, means surface such that said axial forcetends to transport it for applying perturbationsto the body orto particles pastthe slurry application point. The washing liquid held centrifugally to it, means for applying a slurry 90 is forthe purpose of improving the grade or clean and means for applying washing liquid to the inside ness of the heavy mineral in the radially outer layers, of the cylinder (preferably atthe narrower end if it is orfor assisting removal of material either by virtue of tapered) and means for collecting separatelyfrac- the pressure of the liquid, orwhen the applied cent tions from different locations spaced axially along rifugal force is reduced.

the cylinder (such as its opposite ends). The cylinder 95 In collection separated materials may be collected may be a right cylinder, or a frustum or otherwise separately yet at the same end of the cylinder, opti tapered cylinder. onallywith assistance by washing liquid, by a plura The invention also provides a method of separat- lity of blades each extending axiallyfrom an end of ing minerals, comprising applying a slurry containthe cylinderto a respective desired location, the bla- ing the mineral to the inside surface of a cylinder (i.e. 100 des and slurry applicator being arranged to rotate including right cylinders, frusta or otherwise tapered with the cylinder at a rotational speed differentfrom, cylinders) rotating to apply a centrifugal force ex- butwithin 5% (preferably within 1 %) of, the cylin ceeding g atthe surface, perturbing the rotating sur- der's speed; the blades in such a version may be re face, arranging the surface to have a force acting axi- placed by equivalent means, such as jets or curtains ally along it such as by a hydrodynamic pressure 105 of liquid.

gradient, tilt or taper, applying washing liquidtothe The meansfor rotating thecylindermay bea surface atsuch a location that said forcetendsto motor-driven shaft, onwhich a plurality& thetap transport it pastthe slurry application point, and col- ered cylinders may be mounted, for example nested lecting separateiyslurryfractions according totheir outwardlyfrom the same pointon theshaft, orspa different mobilities axiallyalong thecylinder. 110 ced axiallyalong the shaft, or both. Ancillaryappar The separate collections maythus befrom axially atus (such asthe slurryfeed means) is duplicated different locations down the cylinder, such as from appropriately. Material to be treated may be arran each end of the cylinder, preferably continuously. ged to travel through the plurality of cylinders in The perturbations may take any one or more of series or in parallel or partly both.

several forms. For example cyclic variation of the rot- 115 In another preferred version, the invention is a ation speed of the body such as momentary inter- mineral separator comprising a hollow cylinder ruptions to, or acceierations and decelerations sup- rotatable about its axis, which is vertical. The cylin erimposed on, the rotation, or shaking to and fro der has an inward lip, curve ortaperto its lower symmetrically (e.g. sinusoidally) or asymmetrically edge. The minerals separator has means for apply- along an axis (such as the axis of rotation) preferably 120 ing a slurry of the mineral to be separated to the in such that particles adhering to the surface tend to be side of the cylinder and for applying washing liquid conveyed against said axial force, or an orbital mo- to the inside of the cylinder between the lip and the tion (possibly in the plane normal to the axis of rota- slurry application point. The cylinder has meansfor tion). Otherforms of possible perturbation include perturbing it (preferably circumferentially) suffici tilting the axis of rotation, whereby a particle held to 125 entlyto keep the slurry in suspension.

the cylinder experiences an axial force varying The invention in a related aspect is therefore sep cyclically every revolution, and vanes inside the arating minerals by applying a slurry of them to the cylinder and rotating with respectto it, so mounted inside of a hollow spinning verticai-axis cylinder as to force such a particle part-waytowards the with an inward lip, curve ortaperto its lower edge.

upper or narrower end. Axial shaking, tilting and 130 The cylinder is perturbed enough (preferably circum- 2 GB 2 190 609 A 2 ferentially) to keep the slurry in suspension, and 25 cannot be gravity- fed cups as they are shown for washing liquid is applied to it between the slurry simplicity, since the whole assembly 10 is rotating.

application point and the lower edge. The heavy frac- The collectors 21 and 25 could however be annular tion of the slurry is removed either troughs disposed round the periphery of the open (i) continuously from the lower edge, or 70 wider end of the hollow body 1, or otherwise adap (H) by removing the light fraction and (a) under ted to collect (separately, from the brushes 20 and gravity, optionally assisted by flushing liquid, or (b) 24) material thrown out centrifugally from the body mechanically, collecting the heavy fraction. 1.

The invention will now be described byway of ex- In use, slurry is fed through the pipe 16 to the nar- ample with reference to the accompanying 75 rower end of the axially- shaking fast-rotating body 1.

drawings, in which Because the body rotates anticlockwise as drawn at Figures 1, 2 and 3 are schematic views of three dif- 400 rpm while the assembly 10 rotates in the same ferent minerals separators according to the inven- sense at 399.6 rpm, the net effect is equivalent to a tion, rotation of the assembly clockwise at 0.4 rpm inside Figure 4 is a schematic view of part of a minerals 80 the body 1. The slurrythus is shaken (by the shaker3) separator according to the invention, with an altern- while subjectto several g of centrifugal force (in ative drive system, and stead of a mere 1 g of Earth's gravity) and separates Figure 5shows a minerals separator according to into components of which the lightest movethe another preferred version of the invention. most rapidlytowards the wider end of the body 1.

In Figure 1, a minerals separator has a hollow body 85 Increasing the shake speed had the effect of making 1, shown as if transparent, whose inside surface is a even the denser particles more mobile.

frustum. The body 1 is open at its wider end and After about 2 minutes, a g iven element of si urry mounted axially at its narrower end on a shaft 2. The fed from the pipe 16 will be enhanced-g ravity shaken shaft 2 is reciprocated at 7 Hz, amplitude 1 1/2cm ad separated into density bands down the body 1, each side of rest. by a shaker 3 and rotated at 400 rpm 90 and the brush 24will engage all but the heaviest by a motor 4. The body 1 has a frustum cone half- components of that element of slurry. The brush 24 angle of 1', an axial length of 30 cm and an average (aided bywash waterfrom the pipe 15 and from internal diameter of 30 cm. Larger cone angles are other pipes, not shown, nearer each brush) will re effective at higher rotational speeds. move everything it contacts, into the collector 25.

Protruding into the body 1 through its open wider 95 About half a minute later, the heaviest component end is an assembly 10 of feed pipes and scraper (i.e. the highest-density band, containing the metal brushes. Thewhole assembly 10 is mounted on a values in all typical cases) is met bythe longer brush motor-driven shaft 11 and rotates together, in the 20 and washed off into the collector21 forfurther same sense as the rotation of the shaft 2, butat399.6 treatment, The body 1, now brushed clean, then re- rpm. The assembly 10 is fed by stationary pipes 12 100 ceives more slurry from the pipe 16, and the descri through a rotary coupling 1 Oa with slurry and wash bed process carries on continuously. An example of water. The slurry in this example comprises ground a sequence of operations is shown in the table which ore containing small amounts of valuable (high S.G.) follows later.

materiaLthe remainder (lowS.G. material) being The shafts 2 and 11 may be driven from thesame waste,with all particles finerthan 75 microns, half 105 motor (instead of the separate motors described), finerthan 25 microns and quarter finer than 10 mic- with the shaft 11 being nonshaken and powered rons, this ground ore being suspended at a concentr- through a gearbox arranged for a small (e.g. 0.1 %) ation of 50 to 300g, e.g. 150g, per litre of water. The rotational speed differential between the body 1 and solids feed rate is kept at about 50 to 300 g/min,what- the assembly 10). Whetherthe body orthe assembly everthe concentration of solids in the slurry. The 110 rotates the faster is an arbitrary matter of choice as slurry is fed at 1 1/min to the narrower end of the long as the assembly is arranged to deliver slurry hollow body 1 through a slurryfeed pipe 16, and the and to collect, separately, differentiated bands of wash water is fed through a pipe 15 slightly to the slurry.

rear i.e. such that a slurry particle deposited into the The separately collected bands of slurry may be body receives wash water a moment later. Instead of 115 further separated in similar or identical separators.

a single feed pipe 16, slurry can be fed over an arc of Forthis purpose, orfor separating parallel streams up to say 180'of the body. The wash water can like- of slurry, orfor both purposes, the similar or ident wise be fed over an arc. On the other side of the pipe ical separators may be mounted on the same shaft, 16 from the pipe 15 is a long generally axial scraper spaced axially, or nested radially outwards, or stag- brush 20, which can remove matterfrom the whole 120 gered (nested andslightly axially offset), or any com of the inside surface of the body 1 to a collector bination of these.

schematically shown at 21. Between the brush 20 In Figure 2, a minerals separator shown in per and the pipe 15, opposite the pipe 16, is a similar spective has a hollow body 201, shown as if trans brush 24 butslightly shortertowards the narrower parent, whose inside surface is a frustum. The body end of the hollow body 1. The pipes 15 and 16 and the 125 201 is open for exit of fluid at both ends and mounted brushes 20 and 24 are all part of the assembly 10. The axially at its wider end (by means omitted for clarity), shorter brush 24 can remove matterfrom the area on a shaft indicated at 202. The shaft 202 is reciproca which it sweeps, into a collector 25. The brushes 20 ted at7 Hz, amplitude 1112 cm each side of rest, bya and 24are suitably900 apart (though illustrated shaker applying the motion 203 and rotated by a closer, for clarity). In practice, the collectors 21 and 130 motor at 200 rpm in the sense 204. The motor is con3 GB 2 190 609 A 3 nected via sliding bearings to the shaft 202. The being more mobile, can continue to flow, past the shaker acts evenly in each direction (sinusoidally), advancing vane, towards the wider end, helped by but shakers acting with a stronger impulse in one dir- the flow of wash water B. Immediately a given vane ection could be used. The shaft 202 is horizontal. The has receded, the denser particles will tend to'stay body 201 has a f rustum cone half-angle of 1', an axial 70 put'while the water and the lighter particles will re length of 60 cm and an average internal diameter of sume their motion towards the wide end of the body cm. Larger cone angles are effective at higher 201. Overall, the denser particles can be considered rotational speeds. as being steadilyswept, in many short stages, con Protruding into the body 201 through its open nar- trarytothe axial force, towardsthe narrower end of rower end is an assembly 210 of accelerator rings 75 the body 201, whilethe waterand the lighter part 211 and 212 and scrapervanes 213. Thewhole icles can be considered to maketheirway underthe assembly21 0 is mounted on a shaft 202a driven influence of the axial force induced bythetaperof through a gearbox bythe shaft202 and rotates the cylinder despite the vanes towards the wider end together, with the same shake and in the same sense of the body. The matter is thus sorted into valuable as the rotation of the shaft 202, but at 192 rpm. The 80 high density material C collected at the narrower end rings 211 and 212 are fed by stationary pipes with and low density waste D col lected separately at the slurry A and wash water B respectively. The rings 211 wider end. There could be instances where the low and 212 im part a rotational speed to the slurry and density material is valuable, perhaps even more val water, which flow th roug h perforations in the rings uable than the high density material, but it would stil 1 into the body at su bstantial ly the latter's rotational 85 be separated in exactly the same way.

speed and well distributed circumferentially. The The shaft 202 and assembly 210 may be driven slurry in this example comprises ground ore from a from separate motors (instead of the same motor de classifier, containing small amounts of valuable scribed). Whether the body 201 orthe assembly 210 (high S.G.) (usually small-sized material, the remainrotates the faster is an arbitrary matter of choice as der (low S.G. material) (usually larger-sized) being 90 long as the vanes 213 are angled to direct matter waste,withail particles finerthan 75 microns, half pinned to the body generally towards the narrower finer than 25 microns and quarter finer than 10mic- end of the body 201.

rons, this ground ore being suspended at a concentr- The separately collected fractions of the slurry ation of 50to 500g, e.g. 300g, per litre of water. The maybe further separated in similar or identical sep solids feed rate is kept at about 300g/min, whatever 95 arators. Forthis purpose, orfor separating parallel the concentration of solids in the slurry. The slurry is streams of slurry, orfor both purposes, the similar or fed at 1 llmintothe ring 211 situated around the mid- identical separators maybe mounted on the same point of the hollow body 201, and the wash water is shaft, spaced axially, or nested radially outwards, or fed at 1/2 1/min to the ring 212 situated atthe nar- staggered (nested andslightly axially offset), or any rower end of the body 201. 100 combination of these.

The vanes 213 are mounted on four equally spaced In Figure 3, a minerals separator has a hollow body axial arms (onlytwo shown) each carrying ten resili- 301, shown as if transparent, whose innersurface is ently mounted soft plastics vanes41/2cm long afrustum. The body 301 is open at both endsforexit lightly touching the body 201 and angled at 30'to the of fluid and is mounted axially at its narrower end, by circumferential direction of the body (recalling that 105 means omitted for clarity, on a shaft 302, inclined at the body 201 is rotating 8 rpm fasterthan the 20to 60 (say 20) to the horizontal (greatly exaggerated assembly 210 carrying the arms and vanes) so that in the Figure). The wider end of the frustum faces up matter in the body is forced towards the narrower wardly, even its lowest generator running upwardly, end. The vanes on each arm are staggered with re- at an inclination of 1', from narrowerto wider end, spectto the next arm, overlapping by about 1/2 cm, 110 this inclination thus opposing the axial force induced to maximise this effect. bythe taper itself. The half-angle of the frustum is 1 0.

In use, the slurry A is fed via the accelerator ring An asymmetrically acting axial shaker 303 shakes 211 to the midpoint of the axially-shaking fast- the frustum through the shaft 302, with a sharper up rotating body 201. Because the body rotates anti- ward and gentler downward action. A particle on the clockwise as drawn at 200 rpm while the assembly 115 surface of the f rustum thus tends to stay still in 210 rotates in the same sense at 192 rpm, the net ef- space, by inertia, during the sharp upward stroke, fect is equivalentto a rotation of the assemblyclock- but during the gentle downward strokethe particle wise at8 rpm insidethe body 201. The slurrythus is tendsto be held frictionally on, and thus to move as sheared (bythe motion 203) while subjectto several one with, the frustum. Continued asymmetricshak- g of centrifugal force (instead of a mere 1 g of Earth's 120 ing in thisfashion will thustend to move such a part gravity) and separates into components of which the icle progressively towards the narrower end of the lightesttend to move fastertowards the wider end of frustum.

the body 201. Increasing the shake speed had the ef- The frustum is rotated on its axis in the sense 304.

fect of making even the denser particles more SlurryA is continuously applied nearthe middle of mobile, but these normallytend to be pinned cent- 125 the frustum and wash water B is continuously app rifugally to the body 201. lied at an axially similar but circumferentially displa The vanes 213 disturb both the denser sessile part- ced location. The slurry forms a film held centrifug icles and move them a few centimetres towards the allyto the frustum butthe axial shaking is suff icient narrower end of the body 201. The fluid and the ligh- to keep some of its constituents in suspension.

ter particles levitated by the shake/shear action, 130 Those constituents are not otherwise affected by the 4 GB 2 190 609 A 4 shaking. The denser constituents are howevernot the radially innersurface, an upwardiyacting hydro kept in suspension and tend to be pinned centrifug- dynamic pressure gradient, which thus tends to allyto the frustum subjectto the asymmetric shaking carry the lower- specific-gravity particles (waste) with action just described, tending to move them to over- the bulk of the fluid flow. The lip 32 arrests the flow as a heavy-fraction stream C atthe narrower 70 heavier particles into a band 35 on their downwards end. travel, thus both promoting the aforesaid pressure Meanwhile, the rotation, with the taper of the gradient and causing the higher-specific-gravity par frustum, applies an axial force to the film of slurry ticles to overflowthe lip 32 only after some recircula suspension, acting towards the wider end. The water tion and re-sorting (assisted by the vibration). The and the lighter particles, subject more to thisforce 75 action of thewashing waterfrom the pipe 34 is to than to thefriction/shake action, tend therefore to displace waste accidentally entrained with the flowtowards the wider end as a low-density stream higher-specific-gravity particles.

D, this stream (in normal mineral procession) being The valuable higherspecif ic-gravity particles tem the waste. porarily banked into the band 35 overflow down- Figure 4 shows a drive system forthe minerals 80 wardly continuously and are collected. The washing separator, providing an alternative to shaking the water and lower-specif ic-gravity waste particles shaft 2 of Figure 1 and corresponding shafts of other overflow upwardly overthe top edge of the cylinder Figures; a different perturbation is applied to the 31 and are discarded.

body 1 butthe separation proceeds otherwise identi-

Claims (1)

1. cally as described in relation to Figure 1. In Figure 4, 85 CLAIMS the

   body 1 is mounted on a haif-shaft 20 of an auto motive-type differential unit 21. The other half-shaft 1. A minerals separator comprising a body hav 22 is powered by the motor4, which is assisted by a ing a surface having the form of the inside of a cylin flywheel. The'propeliershaft'23 is a shaft which is der arranged when rotating about its axis to have a oscillated. The oscillations add acceierations and de- 90 force acting axially along it, means for rotating the celerationsto the rotation supplied via the haif-shaft body aboutthe axis of the cylinderto applya cent 22 and reversed bythe differential unit21, in other rifugai force exceeding g to said surface, meansfor words the body 1 maybe regarded as rotating applying perturbations tothe body orto particles steadilywith superimposed circumferential oscil- held centrifugallyto it, meansfor applying a slurryof lations. 95 minerals-to-be-separated and optional meansfor In Figure 5, a hollow vertical-axis cylinder31 isset applying washing liquid to the inside of the cylinder, spinning about its axis. The internal diameter being and means for collecting separately fractions from 0.3 to 3.Om and the speed of rotation being a modest different locations spaced axially along the cylinder.

   to 100 rpm, a centrifugal force of the order of 1 Og 2. A minerals separator according to Claim 1, radially outwardly is experienced at the internal sur- 100 wherein the cylinder is aright cylinder, or afrustum, face. This is small enough to allow the Earth's g to or is otherwise tapered.

   have significant effect. The cylinder31 isalsosubjec- 3. A minerals separator according to Claim 2, tedto circumferential vibration at 5to 1 0Hz. At its wherein the cylinder is a frustum whose half-angle is lower edge,the cylinder31 isformed with an in- up to 450.

   wardly curved lip 32, of radial extent 1 to 1Omm. The 105 4. A minerals separator according to Claim 3, lip could alternatively be a sharp flange, at90'or wherein the haif-angle of the frustum is 1/2'to 100.

   otherwise to the cylinder wall. Instead of a we] 1- 5. A minerals separator according to Claim 4.

   defined lip,the lower edge maybe 1 to 1 Omm rad- wherein said half-angle is 1120to 2% iaHy inwards of the upper edge, the intervening cylin- 6. A minerals separator according to any preced- derwall being straight (i.e. tapered), curved (e.g. 110 ing claim. wherein the perturbations are applied by parabolic) or partly both. formed for example by cen- means imparting a cyclic variation of the rotation trifugally casting polymer resin. speed of the body.

   Afeed pipe 33 supplies slurry containing 1 00g 7. A minerals separator according to any of solids suspended per litre of waterto approximately Claims 1 to 5, further comprising a shaker acting to the midpoint (axially) of the cylinder31. The solids 115 and fro along the rotation axis of the bodyforapply are of the size distribution referred to earlier. ing the perturbations.

   Afeed pipe 34 supplies washing waterto the in- 8. A minerals separator according to Claim 7, ternal surface of the cylinder, about mid-way (axiwherein the shaker acts asymmetrically such that ally) between thefeed pipe 33 and the lip 32. particles touching the cylindertend to be conveyed As shown in Figure 5 but grossly exaggerated in 120 againstsaid axial force.

   the radial direction, a film of slurry is held centrifug- 9. A minerals separator according to any preced allyto the internal surface of the cylinder 31 and kept ing claim, wherein the rotation axis is horizontal.

   in suspension bythe vibration. The denser (i.e. 10. A minerals separator according to any of higher specific gravity) particles in the si u rry tend to Claims 1 to 8, wherein the rotation axis is at up to 450 move preferentially radially outwardly (centrifug- 125 to the horizontal.

   ally) and to move downwardly in the boundary layer 11. A minerals separator according to Claim 10, (under Earth's gravity). The vibration, which is circu- when dependent directly or indirectly on Claim 3,4 mferential e.g. bythe means of Figure 4, has a shear- or 5, wherein the lowest generator of the frustum ing action tending to liftthe lower-specific-gravity runs upwardlyfrom narrowto wider end at an inclinparticles radial ly inwardly. The] ip 32 promotes, at 130ation of 11/4oto Wto the horizontal.

   GB 2 190 609 A 5 12. A minerals separator according to Claim 11, tapering the cylinder.

   wherein said inclination is 1/20to 6'. 25. A method according to Claim 22, 23 or24, 13. A minerals separator according to any pre- wherein the speed of rotation of the cylinder is such ceding claim, further comprising an assembly arran- asto apply a centrifugal force of from 5g to 500g to ged to rotate within the cylinder at a relative speed 70 the table surface.

   therein which is small compared with the rotation 26. A method according to any of Claims 22 to 25, speed of the body, the assembly and the body being wherein washing liquid is applied intermittently or equally subject to the perturbations. continuouslyto the cylinder at such a location that 14. A minerals separator according to Claim 13, said force tends to transport it past the si u rry appi ica wherein at least some of the means for applying the 75 tion point.

   slurry and the washing liquid are mounted on the 21. A method according to any of Claims 22to 26, assembly. wherein the rotation conditions are such in relation 15. A minerals separator according to Claim 13 or to the slurry's components that the denser fraction is 14, wherein the assembly comprises a plurality of held centrifugallyto the cylinder relatively immobile blade means each extending axiallyfrom an end of 80 asthe less densefraction departs axiallyfrom it, per the cylinderto a respective desired location for col- mitting theircollection from separate locations.

   lecting separately fractions from different locations 28. A method according to any of Claims 22 to 27, spaced axially along the cylinder. wherein collection of separated materials is con 16. A minerals separator according to Claim 13 or tinuous and separated materials are collected separ 14,wherein the assembly comprises vane meansfor 85 ately, optionallywith assistance bywashing liquid, axially directing matter held centrifugally to the by blades or equivalent means each extending axi body, contrary to said axial force, in repeated steps allyfrom the wider end of the cylinderto a respective each small compared with the axial length of the desired location, the blades and slurry applicator cylinder. being arranged to rotate with the cylinder at a rotati- 17. A minerals separator according to Claim 16, 90 onal speed different from, but within 5% of, the cylin wherein the direction of the forcing is towards the der's speed.

   upper or narrower end of the cylinder. 29. A method according to Claim 22, having all 18. A minerals separator according to any pre- the following features (1) to (3): (1) Minerals are sep ceding claim, wherein the said different locations arated by applying a slurry of them to the inside of a spaced axially along the cylinder are its opposite 95 hollow spinning vertical-axis cylinderwith an inward ends. lip, curve ortaperto its lower edge. (2) The cylinder is 19. A minerals separator according to any preperturbed enough to keep the slurry in suspension, ceding claim, wherein the means for rotating the and washing liquid is applied to it between the slurry cylinder is a motor-driven shaft, on which a plurality application point and the lower edge. (3) The heavy of the tapered cylinders is mounted. 100 fraction of the slurry is removed either 20. A minerals separator according to Claim 1, (i) continuously from the lower edge, or having all the following features (a) to (d): (ii) by removing the lightfraction and (a) under (a) The minerals separator comprises a hollow gravity, optionally assisted by flushing liquid, or (b) cylinder rotatable about its axis, which is vertical. mechanically, collecting the heavyfraction.

   (b) The cylinder has an inward lip, curve ortaper 105 30. A method according to Claim 29, wherein the to its lower edge. perturbing (2) acts circumferentially.

   (c) The minerals separator has means for apply- 31. A method according to Claim 27, wherein ing a slurry of the mineral to be separated to the invane means, rotating within the cylinder at a relative side of the cylinder and for applying washing liquid speed which is small compared with the rotation to the inside of the cylinder between the lip and the 110 speed of the cylinder, direct its contents, in repeated slurry application point. steps each small compared with the axial length of (d) The cylinder has means for perturbing it suf- the cylinder, in the opposite direction to that which ficientlyto keep the slurry in suspension. the less dense fraction tends to take underthe influ 21. A minerals separator according to Claim 20, ence of said axial force.

   wherein the perturbing means (d) act circumferenti- 115 32. A method according to any of Claims 22to 28 ally. or31, wherein the perturbing is done by shaking the 22. A method of separating minerals, comprising cylinder to and fro along its axis of rotation.

   applying a slurry containing the mineral to the inside 33. A method according to Claim 32, wherein the surface of a cylinder rotating to apply a centrifugal shaking is asymmetric such that particles touching force exceeding g at the surface, perturbing the rotat- 120 the cylindertend to be conveyed against said axial ing surface or particles held centrifugallyto it, force.

   arranging the surfaceto have one or more forces ac- 34. A method according to any of Claims 22 to 30, ting axially along it, and collecting separately slurry wherein the separate collections are two, one from fractions according to their different motions axially each end of the cylinder.

   along the cylinder. 125 35. A method according to any of Claims 22 to 34, 23. A method according to Claim 22, wherein the wherein the rotation axis of the cylinder is horizontal.

   force acting axially along the cylinder is a hydro- 36. A method according to any of Claims 22 to 34, dynamic pressure gradient. wherein the rotation axis of the cylinder is at upto 450 24. A method according to Claim 22, wherein the to the horizontal.

   force acting axially along the cylinder is induced by 130 37.A method according to Claim 36, when the 6 GB 2 190 609 A 6 cylinder is a frustum, wherein the iowestgenerator of thefrustum runs upwardlyfrom narrowtowider end at an inclination of 1/4'to 2Tto the horizontal.

   38. A method according to Claim 37, wherein the 5 inclination is 1/Tto W.

   39. A minerals separator according to Claim 1 substantially as hereinbefore described with reference to and as shown in any one of Figure 1 to 3 of the accompanying drawings.

   40. A method of separating minerals according to Claim 22, substantially as hereinbefore described with reference to the accompanying drawings.

   41. Minerals which have been separated by a separator according to any of Claims 1 to 21 or39 or bya method according to anyof Claims 22to 38 or 40.

   Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd, 10187, D8991685. Published byThe Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies maybe obtained.