US3374885A

US3374885A - Method and apparatus for beneficiating minerals

Info

Publication number: US3374885A
Application number: US316372A
Authority: US
Inventors: Floyd J Clawson; Stefano Michael C De
Original assignee: Unifab Inc
Current assignee: Unifab Inc
Priority date: 1963-10-15
Filing date: 1963-10-15
Publication date: 1968-03-26
Anticipated expiration: 1985-03-26

Description

March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS March 26, 1968 F. J. cLAwsoN ETAL. 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15. 1963 '7 Sheets-Sheet 2 March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICITING MINEALS y INV ENT ORS Floyd J @lawson & /I//z'caeZ .6. de ief'ww @/fmf March 26, 1968 F. .1. cLAwsoN ETAL 3,374,885v

METHOD AND APPARATUS FOR BENEFICITING MINERALS 7 Sheets-Sheet 4 Filed Oct. l5, 1963 Ill INVENTORS Maich 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICATING MINERALS 7 Sheets-Sheet 5,

Filed Oct. l5. 1963 March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15, 1963 7 Sheets--Sheefl 6 I v .w

I INVENTOR@ ATT RNEYS March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15, 1965 7 Sheets-Sheet 7 (mi m INVENToRa im' N Fzoydfcmwm {W elMjc/maadfefw ATTORNEYS United States Patent O 3,374,885 METHOD AND APPARATUS FOR BENEFICIATING MINERALS Floyd J. Clawson and Michael C. De Stefano, Lakeland, Fla.; said Clawson assignor to Unifab, Inc., Camden, Tenn., a corporation of Tennessee Filed Oct. 15, 1963, Ser. No. 316,372 11 Claims. (Cl. 209-17) This invention generally relates to the beneficiating of minerals for use as direct products and/or further concentration. More particularly, the invention relates to an improved method and apparatus for beneficiating ores such as phosphate, iron, barite, feldspar, mica and potash in which the ores generally are beneficiated for further concentration. The invention is not restricted to ores alone, however, and in the case of minerals such as sand, limestone and coal, the beneiiciation may result in a direct end product.

Substantially all ores and other minerals are found in their native state admixed with impurities such as clays and other very finely divided or colloidal particles. These impurities are harmful to the mineral product itself, and in particular, hinder the processing of ores.

In the usual process of beneficiating ores or other minerals, the raw mineral material obtained from the natural mineral deposits is processed by washing, screening, etc., to remove trash therefrom and to separate and recover the larger mineral particles. In the case of ores, it is common to recover the raw mineral particles over 1%; inch by this preliminary operation. These larger inch particles are usually suitable for use without further processing. The remaining inch material, however, contains a mixture of the mineral particles and impurities of fine material which must be further processed. The mixture of raw material and liquid is generally referred to as a slurry.

When the raw mineral materials are mixed with Water or other liquid, the very finely divided particles form slimes which interfere with further processing. The slime particles have a large surface and tend to absorb reagents, thereby making the cost of using a reagent prohibitive. Moreover, the slimes cause difliculty in the area of Selectivity of the end product. These slimes and other impurities therefore must be removed in order to make further processing economical. The removal of fine material, including the slimes, is generally referred to as a desliming operation.

Many varied and different methods and apparatus heretofore have been employed to effect the desliming and/or other benefciation of ores and other minerals. Hydrocyclones and deslimers, in particular, are commonly used for such beneficiation, The .prior art methods and apparatus, however, have not proven entirely satisfactory and have been beset with various disadvantages.

Most equipment of this nature is extremely bulky and difficult to handle. A typical ore beneficiating unit, for example, may require as much as 5000 square feet of space. One of the major problems has been to reduce the size and space requirements for such units. Further, the prior art mineral beneficiating methods and apparatus have not been able to recover sufficient amounts of the very small mineral particles. These particles heretofore have been carried away with the slimes.

It is common to employ hydrocyclones in ore or other mineral beneficiating units. A hydrocyclone is a generally cylindrical vessel comprising a truly cylindrical section which merges into a generally conical section. An opening is provided in the bottom or apex of the cone of the conical section, while another opening is provided in a cover plate on the cylindrical section which is coaxial Hee with the apex opening. The opening in the cover plate generally has mounted therein a pipe or tube of definite size extending down into the cylindrical chamber a predetermined distance. The pipe is known as a vortex finder. In operation, a liquid suspension is supplied under pressure tangentially through a feed inlet to the cylindrical section of the hydrocyclone. The suspension is given a sufficient rotational impulse to keep it rotating during its passage through the hydrocyclone. As the swirling stream of liquid aproaches the apex of the hydrocyclone, a portion of it turns and begins to flow toward the opposite or base end of the machine. The heavier fraction of the solids is thrown toward the wall of the hydrocyclone and thereafter flows in a downward spiral to the apex opening whereupon it is discharged. This discharge from the apex is known as the underflow of the hydrocyclone. The lighter fraction of the suspended solids is dragged or pulled into the uprising column in the center of the hydrocyclone whereupon it is discharged through the vortex finder. This discharge from the vortex finder is known as the hydrocyclone overflow.

Due to the high velocity of the swirling liquid suspension in the hydrocyclone and the centrifugal forces created thereby, the surfaces of the hydrocyclone exposed to the moving suspension are subjected to excessive abrasive wear and chemical breakdown, resulting in a relatively short useful life of the hydrocyclone. Attempts have been made to solve this problem by the use of sacrificial linings within the housing of the hydrocyclone. These sacrificial linings usually are bonded to the housing of the hydrocyclone and are of a wear-resistant material, such as rubber. Although these linings have increased the useful life of the hydrocyclone, they nevertheless are also subject to wear and consequently must be replaced in a relatively short period of time. Moreover, the replacing of these linings necessitates a costly curtailment of operations while the repair is being effected.

The operation of a hydrocyclone is readily affected by slight physical and environmental changes such as changing the area of the feed inlet entrance, changing the feed inlet pressure, and ychanging the inside dimensions of the hydrocyclone. A major problem in the use of hydrocyclones has been how to make these changes readily and economically in one hydrocyclone without resort-ing to the use of several different hydrocyclones. There has long been a need in the prior art for a single hydrocy-clone which can be readily changed to a variety of sizes and/ or types as required.

Another apparatus commonly employed in an ore or mineral beneficiating unit is a deslimer. In one type of conventional deslimer, raw feed material which already may have been partially washed and deslimed or otherwise processed is introduced into one end of a long waterlled trough or other container and a deslimed product is subsequently discharged through a bottom opening in the opposite end of thetrough. The desliming of the raw feed material is effected by upwardly flowing water from the ybottom of the trough. As the raw feed material flows along the bottom of the trough in a generally horizontal direction toward the discharge opening, the upwardly flowing water Washes the fines or slime particles from the larger particles of feed material. The removed slimes subsequently are carried upwardly and discharged into an overflow launder disposed about the upper edges of the trou-gh While the deslimed larger particles exit through the discharge opening in the bottom of the trough.

Although the 'above-described conventional deslimer provides a reasonably leffective means of obtaining a deslimed product, it is nevertheless, subject to certain dis- J advantages. It is difficult to obtain the proper amount of control over the operation of such deslimers which is necessary to obtain the maximum degree off desliming. Consequently, an undesirable amount of slimes still remain entra-ined in the deslimed product. More-over, such deslimers must be constructed of a relatively large size in order to obtain the capacity which is necessary in the operation of an efllcient beneciating plant or unit. A major problem has been how to reduce the overall size of such deslimers and still retain a capacity sufficient to handle the quantity of feed material necessary for an eflicient beneilciat-ing operation.

Sumps are commonly employed at various stages in an ore or mineral beneciating process to collect the slurry of raw feed material so that it may be pumped to the next unit employed in the process. For example, when an ore beneilciating unit is initially started, a suflicient amount of slurry must rst be collected in a sump in order to create a pressure head sufficient to operate a suction pump. Suction pumps often air lock and consequently, a certain pressure head is necessary to overcome the air lock to initiate operation -of the pump. The prior art has attempted to solve this problem of creating sulllcient head by constructing high sumps. These sum-ps must be almost completely filled with a slurry bef-ore a sullicient head is created. Consequently, there is always the danger of the sump running over. Also, the high sulmps add to the bulkiness of the beneciating unit.

To overcome the disadvantages o-f the prior art methods and apparatus for beneflciating minerals, it is an object of the present invention to provide `an improved method and apparatus for beneflciating minerals which is efllcient and economical and permits the recovery of a maximum amount of high grade mineral product.

Another object of the invention is to provide an improved apparatus for beneciating ores which is relatively small and compact and yet which has a capacity suflicien-t to meet modern industrial needs.

A further object of the invention is to provide an impr-oved method and apparatus `for de'sliming ores.

A still further object of the invention is to provide an improved hydrocyclone which has an extremely wearresistant liner.

Another object of the invention is .to provide such a hydrocyclone which has a readily removable and replaceable liner.

Yet another object of the invention is to provide an improved hydrocyclone which may be readily altered :to a variety of sizes and/or types as required.

A further object of the invention is to provide such a hydrocyclone having readily replaceable inserts to change the areas of the feed inlet entrance and the apex discharge opening.

Another object of the invention is to provide an improved deslimer which is of a relatively small size and yet has .a capacity sufficient to handle the quantity of feed material necessary for an efficient beneficiation operation.

Still another object of the invention is to provide such a deslimer which may be precisely controlled to obtain the maximum degree of deslim-ing.

Yet another object of lthe invention is to provide an improved meth-od yand apparatus for `desliming which utilizes a positive displacement of the liquid phase to effe-ct a positive desliming.

A further object of the invention is t-o provide an improved liquid .sump which is of a relatively small size and yet is capable of producing a pressure head sufficient to operate a suction pump.

A` still further object of the invention is to provide such -a sump which eliminates the danger -of the liquid in the sump running over While the sufllcient pressure head is created to operate a suction pump.

A preferred embodiment of the apparatus of the present invention generally comprises a feeder for supplying a feed of a ymineral slurry at constant volume and pressure, one or more hydrocyclones for effecting a preliminary particle -size separation .and partial desliming of the slurry, a deslimer for effecting a further desliming of the slurry, and screening means to effect a size separation of the deslimed mineral particles of slurry discharged Ifrom the deslimer. This apparatus preferably is constructed in .the form of .a relatively compact unit which permits ease of handling.

In addition, the apparatus may include means for effecting a preliminary processing of the slurry prior to its introduction into the above-described unit. Such means may include a pri-mary sump for initially receiving the mineral slurry, a primary pump, a feeder for receiving the `slurry from the primary sump and maintaining it under constant pressure, at least one or more first stage hydrocyclones for effecting a preliminary sepa-ration of the slurry into a lighter lines phase and a denser mineral phase which results in -a higher recovery of the denser mineral phase, and a secondary sump for collecting the slurry so .that it subsequently may be delivered to the feeder of the previously described unit.

The hydrocyclone employed 'in the apparatus of the present invention generally includes a body comprised of an outer housing and an inner ceramic liner disposed within said housing, said liner being divided into a plurality of easily removable sections, said body defining a cylindrical Ichamber at its base end which merges into a frus-t-o conical separating chamber at its opposite apex end, an inlet for introducing a mineral slurry tangentially into the cylindrical chamber of said body, means for varying lthe size of said inlet, discharge means coaxial with said body for withdrawing ya lighter fines phase, and open discharge me-ans disposed at the apex end of said body for withdrawing a denser mineral phase.

The deslimer of the apparatus of the present invention generally comprises a tank lfor receiving said slurry, means for injecting a first .auxiliary liqud under pressure horizontally into said t-ank to move the particles in said slurry horizontally therethrough, a porous bottom wall n said tank to permit a second auxiliary liquid -to said bottom wall under .a pressure suflicient to remove the smaller slime particles but not the larger mineral particles -as said second liquid moves upwardly through said tank, means for overflowing and discharging the smaller slime particles from the upper end of said tank, and means for discharging .the larger deslimed mineral particles from the bottom of said tank.

The sump of the apparatus of the present invention generally comprises a tank, an overflow reservoir to receive a liquid upon its initial entry into said sump, said reservoir being situated above and adjacent the upper edge of one of the walls of said tank so that liquid overflowing from said reservoir passes into said tank, a discharge outlet in one wall of said tank, and means opposite said outlet for injecting an auxiliary liquid into said tank toward said outlet to increase Ythe pressure head at said outlet.

In accordance with the method and apparatus of the present invention, a mineral slurry is delivered to the primary sump from where it is fed to a feeder where it is maintained at a substantially constant pressure head. From the feeder the slurry is injected tangentially into the first stage hydrocycloning zone under constant volume and pressure to effect a preliminary separation of t-he slurry into a lighter fines phase and a denser mineral phase resulting in high recovery of the denser mineral phase. The slurry comprised of the underflow of the denser mineral phase is then fed to a secondary sump from Where it is delivered to a second feeder maintained at a substantially constant pressure head. The slurry thereupon is injected tangentially into the second stage hydrocycloning zone under constant volume and pressure to further separate the slurry into a lighter lines phase and a denser mineral phase. The delivery pressure which the slurry has at the entrance to the second stage hydrocyclone is suflicient to cause the slurry to rotate around the portion of the hydrocyclone adjacent the entrance thereof and at least partially impinge upon itself without creating undue turbulence in the entire cylinder adjacent the entrance. This impingement causes a shearing action which scrubs and further deslimes the mineral particles of the slurry. The denser mineral phase from the second hydrocyclone is then delivered to a desliming zone whereupon a first auxiliary liquid is injected under pressure horizontally into the desliming zone to move the mineral phase horizontally therethrough. A second auxiliary liquid is introduced upwardly into the desliming zone to remove the smaller slime particles but not the larger mineral particles. The slurry containing the larger mineral particles is then discharged from the desliming zone into a screening zone whereupon the particles undergo a size separation.

The invention having been broadly described, it will now 'be described in more detail with reference to the accompanying drawings in which:

FIGURE 1 is a schematic liow sheet illustrating the method and apparatus of the present invention;

FIGURE 2 is a front elevation view of an apparatus embodying various features of the present invention;

FIGURE 3 is a side elevation view of the apparatus shown in FIGURE 2;

FIGURE 4 is a cross sectional side elevation view of a hydrocyclone of the present invention;

FIGURE 5 is a cross sectional view along line A-A of FIGURE 4;

FIGURE 6 is a cross sectional side elevation view of a deslimer of the present invention; n

FIGURE 7 is a partial cross sectional View along line B-B of FIGURE 6;

FIGURE 8 is a top plan view showing the perforated bottom of the deslimer of FIGURE 6;

FIGURE 9 is a sectional View of a portion of the bottom of the deslimer shown in FIGURE 8;

FIGURE 10 is a side elevation view of a sump and pump of the present invention with the sump being shown in cross section;

FIGURE 11 is a cross sectional side elevation view .of the reservoir portion of the screen of the present invention; and

FIGURE 12 is a view along line C-C of FIGURE 11.

Referring to the drawings, the raw feed material, such as a mineral slurry, is delivered to a first or primary sump 11. The raw mineral material prior to its delivery to the sump is processed by washing, screening, etc., to remove trash therefrom and to separate and recover the mineral particles over 3A; inc-h. These larger 3%; inch particles are usually suitable for use without further processing. The remaining inch material, however, contains a mixture of mineral particles and impurities which must `be further processed. The raw mineral material is generally mixed with a liquid to form a slurry for further processing.

The sump 11 includes an overfiow reservoir 12 to receive the slurry upon its initial entry into the sump, as best villustrated in FIGURE 10. A side wall 13 of the reservoir is of a reduced size to provide an overflow edge for the slurry in the reservoir to overflow into a tank 14. The reservoir 12 is situated above and adjacent the upper edge of the back wall 15 of tank 14. Back wall 15 is inclined downwardly to permit the smooth flow of liquid from the reservoir to the bottom of the tank. Reservoir 12 and tank 14 are held in position by a framework generally indicated by the numeral 16.

upon its initial entry into the sump and thereafter discharge it over sidewall 13 in order to permit any air entrained in the liquid to escape therefrom. This is important due to the fact that an excess amount of air entrained in the slurry may cause an air lock in the suction pump 19.

The reason for injecting an auxiliary liquid under pressure into the tank through pipe 18 is to create an artificial pressure head at outlet 17. The increased pressure created lby the injection of the auxiliary liquid permits the pump 19 to operate even though the liquid level in the sump is relatively low. This important feature permits the construction of a relatively low sump since the injected liquid creates a sufficient head to operate the pump. Otherwise, it would be necessary to construct a high sumpin order to build up a level of water in the sump sufficient to create a high enough pressure for the pump to operate. Moreover, due to the artificial pressure head which is created, it is not necessary to fill the sump to a high level. rlhis has a further advantage in that it eliminates the possibility of the sump running over.

The slurry is delivered from sump 11 to a feeder 22 by pump 19. A substantially constant pressure head is maintained in feeder 22 by keeping the level of the liquid supply in the feeder relatively constant. The feeder 22 may have a lbypass leading back to the entrance into the sump 11. When the system is initially put into operation, a constant level of fiuid is quickly established in feeder 22 and the excess then goes to the bypass 23 to be delivered 'back to the sump 11. After the system has been put into operation, the pump 19 can be regulated to maintain a constant volume in feeder 22 and the bypass 23 no longer need be used.

From the feeder 22 the slurry is delivered under constant volume and pressure to a first stage hydrocycloning zone 24 to effect a preliminary separation of the slurry into a lighter fines phase and a denser mineral phase, resulting in a high recovery of the denser mineral phase. A partial desliming also occurs in the first stage hydrocycloning zone 24. The first stage hydrocycloning zone includes at least one and preferably a plurality of hydrocyclones. The overflow comprised of the lighter fines phase of the slurry is discharged from the hydrocycloning zone 24 to waste, or alternatively, water reclaimation, While the underow of the hydrocycloning zone comprised of the denser mineral phase is discharged from the hydrocycloning zone and collected in a sump 51. Sump 51 is similar in construction to sump 11 previously described. I

From the sump 51 the slurry comprised of the underow from the first stage hydrocycloning zone 24 is pumped to a feeder 52 by means of suction pump 53. A substantially constant pressure head is maintained in feeder 52 by keeping the level of the liquid or slurry'therein relatively constant. Feeder 52 is provided with a bypass 54 back to sump 51 so that when the level of the liquid in the feeder 52 is sufficient to provide a constant pressure head, the excess may go to the bypass. The slurry is injected from feeder 52 tangentially into a second hydrocycloning zone 55'under constant Volume and pressure for further separation of the slurry into a lighter fines phase and a denser mineral phase. The second stage hydrocycloning zone includes at least one and preferably a plurality of hydrocyclones.

A preferred type of hydrocyclone employed in the first and second stage hydrocycloning zones is comprised of a body 25 which includes an outer housing 26 and an inner ceramic liner 27 disposed therein, as shown in FIGURE 4. The housing 26 may be constructed of any suitable material including, metal, plastic and Fiberglas. The housing 26 may be divided into a plurality of removable sections. Each section of the housing is provided with outwardly extending flanges 28 at its ends yfor connection with adjacent sections. The sections 7 are connected together by means of nut and bolt assemblies 29.

The ceramic liner 27 is similarly comprised of a plurality of sections which conform to the configuration of the outer housing 26. Liner 27 is not bonded to housing 26 but fits loosely therein to permit easy removal and/ or replacement. The ceramic liner sections are slightly longer than the outer housing sections so that when the hydrocyclone is assembled, the sections of the ceramic liner are pulled together in a tight sealing relationship. In addition, a sealing means, such as liquid neoprene, may be disposed between the liner sections to effect a tighter seal. Since the ceramic liner floats freely within the housing, it may readily expand or contract Without braking.

The body 25 generally defines a cylindrical chamber 31 at its upper or base end which merges into a frustro conical separating chamber 32 at its opposite apex end. Integrally connected with the body 25 in the region of its cylindrical chamber end is a feed inlet 33 comprising a passageway 34 and an inlet port 35 opening into the cylindrical chamber 31. The back side wall of passageway 34 is tangential with cylindrical chamber 31, while the opposite side wall of passageway 34 is tapered to an angle of at least and not exceeding 30 with respect to the tangential back side wall. The front side wall of passageway 34 is preferably tapered to an angle of with respect to the tangential back side wall of the passageway. The inlet port 35 preferably is long and narrow to permit the entering slurry to be relatively evenly distributed vertically along a substantial portion of the walls of the cylindrical chamber. The outer end of feed inlet 33 is provided with outwardly extending flanges 36 for connection to a delivery pipe 37. Means are provided for varying the size of the inlet 33 comprising ceramic inserts 45 which are adapted to lit into the bottom of the feed inlet.

The inlet 33 and the cylindrical chamber portion 31 of body are closed at their upper ends by a ceramic cover plate 38 which rests on the upper surface of the ceramic liner section disposed within the cylindrical chamber and feed inlet of the hydrocyclone. In addition, cover plate 39 constituting a portion of the housing, secures the ceramic liner cover plate 38 in place. Separating the ceramic plate 3S and housing cover plate 39 is a rubber gasket 40 which assists in sealing the upper portion of the hydrocyclone against leakage. A vortex nder pipe 42 extends through the housing cover plate 39 and the ceramic liner cover plate 38 into the cylindrical chamber 31 of the body 25 to provide a means for discharging the overflow comprised of the lighter tnes phase of the slurry from the hydrocyclone. The vortex finder pipe 42 may be readily adjusted to any desired predetermined distance into the cylindrical chamber. The vortex nder pipe 42 is coaxial with the body 25.

An outlet 43 coaxial with the vortex finder 42 is provided at the apex end of body 25 for discharging the underflow comprised of the denser mineral phase of the slurry from the hydrocyclone. Outlet 43 is comprised of a removable ceramic insert 44 having an opening therein which is secured to the apex portion of the hydrocyclone by a cylindrical ange member 45.

It is to be noted that the ceramic liner 27 lines the entire inner portion of the hydrocyclone, including the inlet and apex discharge opening, to provide a wearing surface for the slurry passing through the hydrocyclone. Moreover, the upper portion of the ceramic liner 27 disposed within the cylindrical portion and the inlet of the hydrocyclone preferably is constructed as one integral piece. The ceramic liner is much more advantageous than the sacrificial wear resistant liners such as rubber, previously employed in that it has a much longer life. This reduces the necessity of frequent costly curtailment of operations while the liner is being replaced. Another important advantage of having removable liner sections resides in the fact that the sections may be varied to a number of different sizes to alter the physical dimensions inside the hydrocyclone to permit operation under many different circumstances. It is also to be noted that the ceramic insert 44 in the apex of the hydrocyclone permits the size of the apex discharge outlet to be readily varied merely by changing the size of the opening in the insert.

In operation of a hydrocyclone of the type just described, a rotating body of slurry is established and maintained in the confined space of the hydrocyclone. Additional slurry is then continuously delivered tangentially under constant volume and pressure to the rotating body of slurry in the region of the cylindrical end portion of the hydrocyclone. As the body of-slurry rotates in the hydrocyclone, a dual vortical movement is created whereby the outer portion of the rotating body containing the denser mineral phase moves helically along and about the axis of rotation toward the apex of the hydrocyclone while the inner portion of the rotating body containing the lighter nes phase moves helically along and about an axis of rotation toward the cylindrical portion of the body. The slurry is delivered tangentially to the rotating body through an entry zone or passageway having a boundary or wall which gives a directional vector of at least 10 and not exceeding 30 with respect to the line of tangential entry to a portion of the slurry just prior to its tangential entry so that the denser mineral phase of the slurry is immediately thrown'to the outer periphery of the rotating body. The denser mineral phase is then removed as underow at the apex of the hydrocyclone while the lighter fines phase is removed as overflow at the cylindrical base end of the hydrocyclone.

The operation of the tirst and second stage hydrocyclones may be distinguished by the fact that the `first stage hydrocyclones are employed to effect a high recovery of the mineral phase with a limited amount of desliming while the second stage hydrocyclones are of the high impingement type wherein a shearing action occurs which scrubs the mineral particles of the slurry to effect a more complete desliming and separation of the particles. By way of further explanation, in the rst stage hydrocyclones, the slurry is injected tangentially so that it rotates around the cylindrical portion of the hydrocyclone and moves helically downward into the frustro conical portion thereof Without impinging upon itself. In the second stage hydrocyclones, however, the slurry is delivered tangentially to the cylindrical chamber of the hydrocyclone under a pressure sutlicient to cause the entering slurry to rotate around the cylindrical chamber in a manner approaching laminar flow and at least partially impinge upon itself without creating undue turbulence in the entire cylindrical chamber. This impingement causes a shearing action among the particles of the slurry which scrubs the denser mineral phase of the slurry. This shearing and scrubbing action not only further deslimes the slurry, but also prepares the denser mineral phase of the slurry which is removed as the underflow from the hydrocyclone for a further desliming action. In eiect this preparation amounts to a partial loosening of the slime particles which still remain attached to the particles of the denser mineral phase so that the denser mineral phase particles may be more easily deslimed in a subsequent desliming operation.

Besides the difference in delivery pressure between the first stage hydrocyclones and the second stage hydrocyclones, the size of the inlet of the second stage hydrocyclone is reduced by inserting the removable inserts into the bottom of the feed inlet. This reduction in size of the inlet of the second stage hydrocyclones combined with the increased delivery pressure causes the slurry entering tangentially into the second stage hydrocyclone to rotate completely around the cylindrical chamber of thelfhydrocyclone and at least partially impinge upon itse The overflow of the second stage hydrocyclone 55 is delivered to a deslimer 60 for further desliming While the underflow thereof is discharged to the sump 11 for reintrodu-etion into the system or, alternatively, discharged to waste.

The deslimer includes a generally V-shaped elongated tank 61 having a feed inlet 62 adjacent. the `top at one end thereof and a deslimed product discharge outlet 63 at the bottom of the opposite end of the tank. A plurality of spaced baffles 64 extend downwardly from the upper edge of thetank 61 and terminate at a point intermediate the top and bottom wall 65 thereof to form a channel 66 immediately .above the bottom for the passage of the particles of the slurry through the tank to the discharge outlet. The bottom wall 65 of the tank is porous or perforated to allow an auxiliary liquid to be introduced up wardly into the tank through the bottom. Preferably, the bottom wall `65 is comprised of a perforated plate 68 covered by a layer of perforated neoprene material on its top and bottom sides thereof as shown in FIGURE 9.

The auxiliary liquid is supplied under pressure to the bottom 65 by means of a liquid supply manifold 67 attached to the underside of the bottom wall. The manifold 67 is divided into a plurality of compartments 70 by means of spaced partitions 71. Liquid is individually supplied to each of the compartments 70 by means of conduits 72 connected to a liquid supply source. Valve means 73 are provided for individually controlling the pressure of the liquid entering into each compartment 70. Auxiliary liquid also may be injected under pressure horizontally into the tank 61 by means of an injector pipe 74 situated adjacent the bottom of the inlet end of the tank. The horizontally injected liquid moves the particles of the slurry in the tank horizontally therethrough toward the discharge outlet 63. The pressure of the horizontally injected auxiliary liquid may be controlled by valve means 75.

A slimes discharge launder 76 is disposed about the upper longitudinal edges of the tank 61 to collect the slimes which flow over the upper edges of the tank. The launder 76 is inclined downwardly toward the discharge end of the tank.

Means are also provided for controlling the rate of discharge of the deslimed particles through the discharge outlet 63 of the tank comprising an elongated control rod 77 having a hollow rubber covered stopper 78 at its bottom end an an adjusting wheel 79 at its upper end. The upper end of control rod 77 is threaded to permit the control means to be screwed downwardly or upwardly to control the rate of discharge of the deslimed particles through the discharge outlet. The control rod is attached to the tank 61 by means of bracket -assemblies 81.

The discharge outlet 63 includes a Well portion 82 having a rubber lined pipe 83 connected at its bottom end thereof. The bottom end of the well 82 and the pipe 83 are connected together by bolt assemblies 84 passing through flanges 85 on the bottom end of the well and a flange 86 extending outwardly from the body of the pipe.

In operation of the deslimer, a mineral slurry is delivered to the feed inlet 62 of the deslimer from where it descends to the bottom of the tank 61. A first auxiliary liquid is injected under pressure horizontally into the tank through pipe 7,4 to move the particles in the slurry horizontally through the tank. A second auxiliary liquid isintroduced upwardly into the tank through the porous bottom wall 65 under a pressure sufllcient to remove the smaller slime particles but not the larger mineral particles of the slurry upwardly through the tank to the discharge launder 76. The larger mineral particles continue their generally horizontal movement through the tank to the discharge outlet. v

By adjusting the relative pressures of the-horizontally injected auxiliary liquid and the upwardly flowing auxiliary liquid, it is possible, to obtain very precise control over the removal of the small slime particles from the 10 slurry passing through the tank. For example, if the pressure of the horizontally injected liquid were relatively high in comparison with the pressure of the upwardly flowing liquid, substantially all of the particles in the slurry would .be discharged from the tank with a minimum amount of desliming occurring. Similarly, if the pressure of the upwardly flowing liquid introduced into the tank were relatively high in comparison to the pressure of the horizontally injected liquid, substantially all of the particles would be discharged into the overflow launder with a minimum amount of recovery of the larger deslimed particles from the bottom of the tank.

As shown by the arrows in FIGURE 6, when the pressures of the two entering auxiliary liquids are properly adjusted for maximum desliming efficiency, thev particles of the slurry passing through the tank are given an upward velocity vector as well as a horizontal vector so that they tend to move upwardly during their horizontal passage through the tank. The smaller slime particles are discharged into the overflow launder while the medium sized particles tend to strike the bailles in the upper portion of the tank and be deflected downwardly into the flow of mineral particles being discharged from the bottom of the tank. The heavier particles continue their generally horizontal path through the channel formed in the bottom of the deslimer.

In the desliming operation just described, there is `a multi-displacement greater than one of the liquid phase of the slurry which effects a positive desliming under conditions approaching maximum efficiency. A major advantage inherent in the deslimer of the present invention resides in the fact that a relatively small unit can deslime a quantity of slurry sufficient to meet modern-day industrial needs. For example, a unit 3' x 8 x 4 high can effectively deslime up to 150 tons per hour.

The overflow of slime particles from deslimer 60 is dis charged back to the sump 51 for reintroduction into the second stage hydrocycloning zone, while the deslimed underflow of mineral particles 'from the ydeslimer is passed through screening means 90 to effect a particle size separation. It is to be noted, however, that it is not necessary to further screen the deslimed particles upon their disch-arge from the deslimer. The screening operation` is required only if it is desired to separate the particles into various sizes for further processing or beneficiation. As shown on the schematic flow diagram of FIGURE 1 and in FIGURE 2, a plurality of screens may be employed in combination to effect the desired particle size separation.

Referring now to FIGURE 11, each screening unit includes an inclined screening deck 91 of any `desired screen size and an overflow reservoir 92 situated above and adjacent the upper edge of the screening deck. A baille means comprising an angle iron 93 extends substantially across the entire width of the reservoir 92 adjacent the back wall 94 at the bottom thereof. The lower end of baille 93 is spaced slightly from the bottom 95 of the reservoir to provide an outlet for an `auxiliary liquid supplied to the back of the angle iron through supply conduit 96. The pressure and volume of the auxiliary' liquid is controlled by valve means. The front wall 97 of reservoir-92 has an overflow lip 98 on its upper end thereof and is of a reduced height to permit the liquid in the reservoir to overflow onto the screening deck 91. One or more freely swinging plates 99 may be disposed immediately above the screening deck 91 to assist in evenly distributing the liquid from the reservoir 92 over substantially the entire width of the screening deck.I Arranged below the screening deck 91 is a collection hopper 103 for collecting the particles which pass through the screening deck.

In operation of the screening unit 90, the slurry containing the particles to be separated is initially collected in the reservoir 90 from where it overflows onto screening deck 91. An auxiliary liquid is introduced into reservoir 92 behind the baffle 93 to repulp the slurry in the reservoir and assist in lifting the mineral particles in the slurry over the overow edge or lip 98. The mineral particles in the slurry have a tendency to be unevenly distributed in the reservoir 92 when the slurry is collected therein. lf this situation is not corrected, the particles will also be unevenly distributed when the slurry is overowed to the screening deck 91, thus interfering with maximum screening eiciency. The introduction of the auxiliary repulping liquid substantially alleviates this problem. The baffle 93 serves to evenly distribute the incoming auxiliary liquid substantially across the entire width of the reservoir, thus causing the mineral particles in the slurry to spread evenly across the entire width of the overflow edge as the slurry is discharged from the reservoir.

In a typical screening installation employing a pair of screens in combination, the first screen would remove the -35 mesh particles. The second screen would remove those particles between -16 mesh and -l-35 mesh, with the oversize Igoing to storage.

In constructing a mineral beneficiating Iplant utilizing the method and apparatus just described, it has been found desirable to combine various elements of the apparatus in a relatively compact unit which is easy to transport and handle. FIGURES 2 and 3 illustrate one such compact unit 101. As shown in these figures, a feeder 51, one or more second stage hydrocyclones 55, a deslimer 60 and a plurality of screenin-g units 90 are combined into a compact unit 101 supported by frame structure 104. An effective benefication of a mineral slurry can be obtained by employing just the elements included in this structural unit, although for the highest degree of beneficiation it is desirable to use the entire method and apparatus previously described. Using just the last-named unit, however, a feed of mineral slurry is introduced into feeder 51, from where it is supplied under constant pressure and volume to one or more hydrocyclones 5S where a scrubbing and shearing of the particles takes Iplace to effect a preliminary desliming and further prepare the particles for a subsequent desliming operation. The overflow of the hydrocyclone is discharged to waste, while the underflow is supplied to a deslimer 60. The overflow of slime particles from deslimer 60 may be discharged back to the constant head feeder 51 for reintroduction into the system, while the underflow of deslimed particles is passed through the screening units 90 to effect a particle size separation.

A mineral beneficiating unit or plant constructed according to the principles of the present invention permits a substantial saving in fabrication costs, replacement costs and operational and maintenance costs. Moreover, such a plant may be constructed in a relatively small space as compared to most mineral beneficiating units presently used. For example, a typical prior mineral beneficiating plant requires as much as 5000 square feet of space, whereas a mineral beneficiating plant constructed according to the principles of the present invention requires a space of as little as 50 to 75 square feet. In addition, the present invention permits the recovery of deslimed particles down to the micron size.

While the invention has been described with particular reference to specific preferred embodiments, many other modifications may be made by persons skilled in the art without departing from the scope of the invention which is defined solely by the appended claims.

What is claimed is:

1. A method of beneficiating minerals which comprises:

delivering a slurry of a mineral to a hydrocycloning zone under constant volume and pressure to separate said slurry into a lighter fines phase and a denser mineral phase,

delivering said denser mineral phase to a desliming zone,

injecting a first auxiliary liquid under pressure horizontally into said desliming zone independently of said denser mineral phase to move said mineral phase horizontally therethrough,

introducing a second auxiliary liquid upwardly into said desliming zone under a pressure sufficient to remove the smaller slime particles but not the larger mineral particles,

and recovering the larger deslimed mineral particles from said desliming zone.

2. A method as defined in claim 1 wherein said hydrocycloning zone comprises two hydrocycloning stages in series, each of said stages separating feed slurry fed thereto into a lighter fines phase and a denser mineral phase, the slurry of said mineral delivered to said hydrocycloning zone serving as feed slurry for said first stage, the denser mineral phase from said rst stage serving as feed slurry for said second stage and the denser mineral phase from said second stage serving as feed slurry for delivery to said desliming zone.

3. An apparatus for beneficiating minerals comprising:

feeder means for supplying a feed of a mineral slurry at constant volume and pressure,

a hydrocyclone for effecting a preliminary particle size separation into a lighter lines phase and a denser mineral phase of said mineral slurry,

means for delivering feed slurry from said feeder means to said hydrocyclone,

a deslimer,

means for delivering the denser mineral phase of said slurry from said hydrocyclone to said deslimer,

means separate from said denser mineral phase delivery means for injecting a first auxiliary liquid under pressure horizontally into said deslimer to move the particles in said slurry horizontally therethrough,

means for supplying a second auxiliary liquid upwardly into said deslimer under a pressure sufficient to remove the smaller slime particles but not the larger mineral particles,

means for delivering the overflow of slime particles from said deslimer back to said feeder means for reintroduction into said hydrocyclone,

and means for discharging the larger deslimed mineral particles from said deslimer.

4. An apparatus as defined in claim 3 which includes screening means lfor effecting a size separation of said deslimed mineral particles discharged from said deslimer.

5. An apparatus as defined in claim 4 wherein said screening means comprises at least one inclined screening deck, a reservoir having an overflow lip overhanging the upper edge of said screening deck, baffle means extending substantially across the entire width of said reservoir adjacent the bottom thereof and connected to the wall opposite said overflow lip, and means for introducing an auxiliary liquid through said one wall behind said bafe means, said baille means serving to distribute said auxiliary liquid evenly across the width of said reservoir to facilitate lifting and effecting an evenly distributed overflow of the contents of said reservoir onto said screening deck.

6. An apparatus Ifor positively desliming a mineral slurry comprising:

a tank,

inlet means for feeding a mineral slurry to said tank,

means separate from said inlet means for injecting a first auxiliary liquid under pressure horizontally into said tank to move the particles in said slurry horizontally therethrough,

a porous bottom wall in said tank to permit a second auxiliary liquid to be introduced upwardly into said tank,

means for supplying said second auxiliary liquid to said bottom wall under a pressure suicient to remove the smaller slime particles but not the larger mineral particles as said second liquid moves upwardly through said tank,

means for overfiowing and discharging the smaller slime particles from the upper end of said tank,

and means for discharging the larger deslimed mineral particles from the bottom of said tank.

7. An apparatus for positively desliming a mineral slurry comprising:

a tank,

inlet means for feeding a mineral slurry to said tank,

means separate from said inlet means for injectin-g a first auxiliary liquid under pressure horizontally into said tank to move the particles in siad slurry horizontally therethrough,

means for supplying said second auxiliary liquid to said bottom wall under a pressure sufficient to remove the smaller slime particles but not the larger mineral particles as said second liquid moves upwardly through said tank,

a plurality of spaced baffles extending downwardly in the upper portion of said tank and terminating at a point intermeidate the top and the porous bottom wall thereof to form a channel immediately above said bottom wall for the passage of the larger mineral particles of said slurry,

an overflow launder disposed about the upper edges of said tank to discharge the slime particles removed by said upwardly flowing second liquid,

and an outlet in the bottom at one end of said tank for discharging said larger deslimed mineral particles.

8. An apparatus as defined in claim 7 which includes means for controlling the rate of discharge of said deslimed mineral particles.

9. A method for positively desliming a mineral slurry which comprises:

introducing said slurry into a tank,

injecting a first auxiliary liquid under pressure horizontally into said tank independently orf said slurry to move the particles in said slurry horizontally therethrough,

introducing a second auxiliary liquid upwardly into said tank under a pressure sufficient to remove the smaller slime particles but not the larger mineral particles of said slurry,

overflowing and discharging said slime particles from the upper end of said tank, and

discharging the deslimed mineral particles from the bottom of said tank.

10. A method as defined in claim 9 wherein the volume of said first and second auxiliary liquids supplied to said tank is sufficient to effect a multi-displacement greater than one of the liquid phase of said slurry initially introduced into said tank.

11. A screening unit for effecting a size separation of mineral particles contained in a slurry comprising:

an incli-ned screening deck,

a reservoir having an overflow lip overhanging the upper edge of said screening deck,

a baille means extending substantially across the entire width of said reservoir adjacent the bottom and connected to one wall thereof,

and means for introducing an auxiliary liquid behind said baffle means through said wall, said baille means serving to distribute said auxiliary liquid evenly across the width of said reservoir to facilitate lifting and effecting an evenly distributed overflow of the contents of said reservoir onto said screening deck.

References Cited UNITED STATES PATENTS 439,961 11/1890 Lewis 209-244 2,420,180 5/1947 Laughlin 209-454 2,735,547 2/1956 Vissac 209-211 2,779,469 1/1957 Harris 209-211 3,068,802 12/1962 Costello 103-113 3,071,249 1/1963 Rains 209-12 X 3,086,654 4/1963 Hollingsworth 209-12 X 3,129,173 4/1964 Schulze 209-512 3,136,723 6/1964 Erwin 209-211 X 3,207,310 9/ 1965 Yes-berger 209-211 X 3,261,559 7/1966 Yavorsky 209-158 X 1,312,098 8/1919 Ceruti 209-173 3,008,574 11/1961 Clawson 209-12 3,008,575 11/1961 Clawson 209-12 FOREIGN PATENTS 559,092 6/ 1923 France. 1,211,294 10/1959 France.

FRANK W. LUITER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CGRRECTION Patent No. 5,374,885 March 26, 1968 Floyd J. Clawson et al.,

It is certified that error' appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4 line 39 for "n" read in Same-line 39 after "liquid to" insert be introduced upwardly into said tank, means for supplying Said second auxiliary liquid to Signed and sealed this 15th day of July 1969. n

(SEAL) Attest:

Edward M.F1etcher,1r. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

Claims

3. AN APPARATUS FOR BENDFICIATING MINERALS COMPRISING: FEEDER MEANS FOR SUPPLYING A FEED OF A MINERAL SLURRY AT CONSTANT VOLUME AND PRESSURE, A HYDROCYCLONE FOR EFFECTING A PRELIMINARY PARTICLE SIZE SEPARATION INTO A LIGTER FINES PHASE AND A DENSER MINERAL PHASE OF SAID MINERAL SLURRY, MEANS FOR DELIVERING FEED SLURRY FROM SAID FEEDER MEANS TO SAID HYDROCYCLONE, A DESLIMER, MEANS FOR DELIVERING THE DENSER MINERAL PHASE OF SAID SLURRY FROM SAID HYDROCYCLONE TO SAID DESLIMER, MEANS SEPARATE FROM SAID DENSER MINERAL PHASE DELIVERY MEANS FOR INJECTING A FIRST AUXILIARY LIQUID UNDER PRESSURE HORIZONTALLY INTO SAID DESLIMER TO MOVE THE PARTICLES IN SAID SLURRY HORIZONTALLY THERETHROUGH, MEANS FOR SUPPLYING A SECOND AUXILIARY LIQUID UPWARDLY INTO SAID DESLIMER UNDER A PRESSURE SUFFICIENT TO REMOVE THE SMALLER SLIME PARTICLES BUT NOT THE LARGER MINERAL PARTICLES, MEANS FOR DELIVERING THE OVERFLOW OF SLIME PARTICLES FROM SAID DESLIMER BACK TO SAID FEEDER MEANS FOR REINTRODUCTION INTO SAID HYDROCYCLONE, AND MEANS FOR DISCHARGING THE LARGER DESLIMED MINERAL PARTICLES FROM SAID DESLIMER.