US2135957A - Concentration - Google Patents

Description

Nov. 8, 1938. N c, E. wUENscH 2,135,957`

,m Frm/7 Wafer W BY l Y n ATTORNEYS c. E. wUENscH 2 Sheets-Sheet 2 mw.. v N5 S x ,Q t 4 kb mw Patented Nov. 8, |1938,

UNITED STATES ,PATENT ori-#ICE CONCENTRATION Charles Erb Wuensch, South Orange, N. I., as-

lignor to Wuensch Hetero Concentration Process Company, Wilmington, Del., a corporation l oi Delaware Application April s, 1935, serial No. 15,217

Claims.

aration of two or more minerals or other solids` having different specific gravities' by employing gravitational forces in the presence of a heavy iluid.

In the heretofore vcustomary practice of ore Y dressing and allied arts,I mixtures of mineral particles having different* densities have been separated by adding the mixture to a uid having a density intermediate the densities of the minerals to be separated. Under these conditions the mineral particles having a'density greater than that of the :duid tend to sink, whereas mineral particles which are lighter than the fluid tend to float. The products are thus separated, and may be withdrawn, separately from different zones in the uid medium.

The term iiu'id is used here to include true liquids, such as aqueous salt solutions ofhigh specic gravity and heavy organic liquids such as tetrabromethane (CzHzBri) as well as multiphased mixtures of finely divided solids with liquids, usually referred to as suspensions.

Mineral separating processes employing heavy uidshave presented attractive possibilities becauselo'f .their apparent simplicity, and promising results have been obtained when some of these processes have been employed in the laboratory under carefully controlled conditions.A However, duplication ofi these results in commercial practicehas been impossible except in rare instances. Processes employing heavy organic liquids such as tetrabromethanel have not come into commercial use because the relatively high `cost of such 40 liquids usually requires a high initial 'investment and excess replacement costs, for in commercial operations a substantial loss of the separating medium is almost inevitable. Commercial application of. processes that employ heavy salt solutions for mineral separation has been handicapped by the presence of at least three outstanding disadvantages:

(1)` The capital expenditure involved in employing large volumes of such solutions. (2) The cost of solution losses in the operation .of the process.

:(3) The fact. that such solutions become contaminated or diluted in commercial use. In order to restore the solutions to the proper concen- 56 tration, evaporation is necessary, and this entails large expense. Furthermore, removal of contaminants without removing the necessary salts which impart the necessary increase in density to the solutions is frequently impossible, and costly .in any event. 5

Commercial examples of processes employing aqueous suspensions oi finely divided solids in place of true heavy liquids have met withsome success. Aqueous suspensions of finely ground clay, galena, hematite, barytes, silica, and mix- '10 vtures of these.and other minerals have been prepared. Such suspensions are not subject to the aforementioned objections in that they are-less expensive, so that ilrst costaud the cost oi losses are relatively less. Suspensions possess a fur- 15 ther advantage over true liquids in that they may be restored from a diluted state by settling or fdtration, which are less expensive than the evaporation required to remove excess liquid from true Solutions. 2Q

Accompanying these advantages which the use of suspensions afford there are, however, serious disadvantages. Unless the suspended solid particles are so ne as to be practically colloidal, they tend to settle out, so that the density through 25 a column of the suspension varies. Unless means are taken to prevent such settlement, the delicacy of the separation is deleteriously affected, not only by the variation in density from top tobottom' of the-column, but also by the fact that the 30 lpari-.isles crowd into the bottom o f thecolumn, "..where'linstead of exerting an unimpaired and delicate buoyant eifect, they form a mat which y prevents separation of the heterogeneous mixture. Lastly, for any given density, a suspension is 35 usually considerably more viscous than an equivalent true liquid, so that hindrance to separation Y may be excessive.

Separating processes employing suspensions have been at least partially successful in sepa- 40 rating constituents having a marked diiference in density. Thus, such processes have been emplpyed for the separation of coal from slate and pyrite, but have failed to accomplish an adequate separation in commercial practice when there was 45 but a slight diiference in the density of the minerals to be separated. 'Ihis failure may be attributable to the following and other factors:

(1) Improper average density of the suspension. 50

(2) Variation in density throughout the suspension.

(3) Excessive viscosity ofthe suspension. (4) Coarse particle sizeof the solids comprising the suspension.` Y t water valve. Becauseo! the fact that the Selena .control will depend, of course, upon the difference in speciiic gravity between the minerals to be separated. When this difference 'is small the density regulator may be made correspondingly delicate by increasing the sensitivity of the hydrometer employed.

The mineral aggregate to be' separated (designated on 4the ilow sheet as,or) is first screened and washed with water in an appropriate device such as a trommel, to remove the bulk of the fine material. The size of the material retained on the screen will depend in some measure upon the nature of -the' mineral aggregate. vIn the treatment of Joplin jig tailings containing about 1.5 to 2.0 percent of zinc in the form of sphalerite, it has been found that the materiaLshould range in size from V2 to inch down to 20 mesh (Tyler scale). 'I'he fines produced by the trommel-may be wasted, or if the practice is economically Vjustiiled they may-be ground and treated by flotation or other appropriate methods. T he oversize from the-trommels in a clean and slightly moist condition is transported to aseparator -of novel design as shown on Fig. 1.

i Washing the aggregate and supplying it to the separator in aslightly moist condition is desirable for several reasons, viz.,

(l) 'Soluble contaminants are thus removed.

4(2) lMaterials are removed which are too tine to be separated by heavy fluid methods because of the excessive surface exposed per unit of `volume.

(3) The wet surfaces of the aggregate reduce any deleteriousenect of adhesion between particles of the mineral aggregate and the particles comprising the suspension or medium, at the same time facilitating removal of entrained medium from the products made in the separator.

(4) The presence of a `slight amount of mois- .ture dilutes'the medium .in the top of the separator, thus permittingv light minerals to be immersed in the medium in the first instance so that they do not forma iloating mat which -wculd block the fall of heavy particles which follow.

When only two products are to'be. separated', I

`an arm 23 which extends throughs hutch 24. A

drain pipe 25 is provided at the bottom of the hutch. -The; bottomof thepipe 2| is connected to a housing 25, which is inclined upwardly and extends to a point slightly above vthe top of the conical chamber.- A conveyor 21 provided with scrapers 28 is positioned within the housing and' 'through thel pipe 2|.

'I'he drain pipe 25 is equipped with a solenoid Voperated valve 29 and drains -into an agitator box 30 in which a hydrometer 3| of an automatic.

density regulator is located. This- `density regulator is similar to that located at the conditioner outlet and lcomprises a light 32,' a shield 33, a photoelectric cell u, a current source 35 and the solenoid operated valve 29. The agitator box should be so constructed asi@ provide alquiescent zone for the hydrometer without, however, providing a space in which substantial settlement oi solids can occur.

-In operation, moist oversize fromthe trommel and medium of substantially constant density and consistency are 4run continuously into the top of the separator near its center. The agitator 20- is revolved slowly by a chain or other appropriate means. 'I he peripheral speed of the blade tips should not exceed 150 feet per minute. Separation begins immediately, the light minerals tend-v ing to rise and ilowvoutwardly due to buoyancy exerted by the medium of galena slime /a'nd to the slight centrifugal force induced by /the agitator. Under the influence ci these rces the light minerals, designated on the o sheet as tai1ings,`pursue an ascending spiral' pathand overflow into the peripheral tailings launder accompanied by a portion of the medium. heavier minerals or concentrates sink through the cone into the pipe 2|, and come within the iniluence of the vibratingscreen, the function of which is to prevent crowding" or matting of the concentrates and of the galena particles. Unless the washing of the material from the trommel has been perfect and the'ore is unusually hard sg that no attrition occurs in the separator, a small amount of relatively ilne heavy mineral particles will tend to settle alngwith a portion of the galena linthe medium, thus increasing the bottom density, 'aggravating the tendency for crowding, and thus interfering with the separa- 'tion. The vibrating screen 22 is suiiiciently coarse to permit the iine mineral particles (due to attrition orr imperfect washing) together with coarse galena particles to pass outinto the hutch 2l and thence through the drain pipe 25 and the valve 29 into the agitator boxl 30. The' valve 29 is so constructed that it is never completely closed. When the density of the material drain- *ing outfof the hutch ris'es toa predetermined point which indicates that crowding or excessive bottom density is about to occur in the pipe 2| or in the Vbottom oi'tvthe conical chamber, the.

density regulator operates to open the valve still further .and permit lthe outow of the material which is about to cause .the-crowding. When the density ofthe'material leaving the hutch returns to normal the hydrometer drops; 'the circuit of the densit'yregulator is broken; and the The valve, under the iniluenc'e of.-an 'appropriate spring or counterweig'ht,` resumes its normal opening. It-will be apparent that` the feature of the invention whereby a portion of -the medium 'contaminated with ilne concentrate is continuously withdrawn 'from the' separator at a rate depending upon the densityof the material withdrawn is yalso applicableI to processes .in which the separating medium o r heavy 'fluid is a tru heavy'liquid instead of a suspension. l v

When the amount of finev concentratedrained out of the hutch warrants recovery, or when the contamination 'which would result from the presence of the concentrate! in the galena slime re- 15 fine concentrate ca'n be tolerated, and if th amount o f this 'ilne 'concentrate does not warrant recovery,'the screen 35 can be eliminated and the outflow from the agitator box may be returned to the ball mill for further grinding,

or to the thickener.

dilute galena' The coarse concentrates falling through the,

conical chamber and the pipe 2| arepicked up by the conveyor and dragged out above the level of the medium in the drag housing; Some galeria 'accompanies these coarse concentrates, so that drainage and washing on a screen are necessary. The coarse.concentrates are removed from the upper surface of the screen and sent to further processing. The galena is returned to the circuit ashereinafter described. 4

The tailings are removed from the peripheral trough atvthe top of the separator and subjected to screening and washing to remove galena. The galeria is returned to the separating circuit. The tailings (assuming that further treatment is' vnot economical) are transported to the dump.

As shown on' Fig.A l, the draining and washing of the concentrates and tailings in order to produceclean products and to recover the rgaleria slimes are subjected to the following treatment:

' The concentrate and tailings are transported r respectively across screens 3l and 38 of appro-- priate mesh. Such medium as will 'drain oif without the addition of water is permitted to pass through tacles 39 and lll, andA is returned in an undiluted condition to the sump. The drained concentrates and tailings next pass respectively -over screens Il and I2 under water sprays 43 and 4l. The water for these sprays is the slightly turbid overow from the thickener. The @partially washed concentrates and tailings are given a nal washing under fresh water sprays 45 and 4B, and are discharged respectively from the screensll and 42 ina slightly moist condition, i. e. containing about 3 to 5% of water. The dilute medium products resulting from the dual wash'-l ing`treatment of concentrates and tailings arel passed respectively throug'h finer screens 41 and I8 (say 50-80 mesh) in .order to remove any coarse material which would contaminate the medium circuit?, i. e. Vthe circulating suspension of galena. Because the screening of the ore is not perfect and because the screening and washing are advantageously conducted on moving or vibrating screers, some attrition occurs and a secondary screening. of the dilute mediumV is usually necessary before it is returned to the circuit.A

In this way, the sandy material will not prevent the maintenance of optimum conditions in the separator. The sandy concentrates removpd in this secondary screening operation are recovered. The sandy tailings are wasted, or subjected to further treatment. which the nsand has been removed is returned to the thickener.

Appropriate reagents to promote settling, such as lime or alum, may be added to the 'pulp in the sion are amenable to tation (as in the oase with galena and m other minerals with 'metallic surface) there is a tendency for a mineral bearing frotn to form m the surface of the thickener or at other points in the circuit. Froth formation is-objectionable, but it may 'bemlnlmized by adding appropriate depressing agents t0 the circuit.

'I'he thickener overflow is run into a trap 49 from the top o f which any froth may be skimmed.A

After appropriate treatment to remove oleaglnous substance. the solidconstituents of the froth may4 be returned tothe medium or suspension. Water for the sprays employed in the iirst washing of the concentrate and tailings is withdrawn from the bottom ofthe'trap. The controlled excess waterv 'overilows from the trap and is sent to settling ponds (not shown) yor to other approprlate treatment. galena or other valuable solid-- is such as to warrant recovery. The bleeding oi! of this controlled' excessfwater at this point prevents an "undue accumulation 'of deleterious soluble conthe screens into separate recep- The dilute medium' fromA thickener. In commercial operation, la smallamount of oil almest inevitably lealrs into the suspension or separ ting medium at some point in the circuit. If the solid or solids in suspentaminants in the circuit.

In the event that the mineral -aggregate undergoing treatmentis such that more than two classes of products should bev separated from each other, I prefer to employ a novel separating apparatus of my invention as illustrated in Fig. 2. 'I his apparatus comprises a trough 50 having a gently sloping bottomA 5I, and adapted to be partially 'filled with the separating medium o`r suspension employed. Underneath the deep end of the trough is located a-jig chamber 52 equipped witha screen 53 of such mesh that a jig bed of concentrates will be retained thereon. A movable piston 5I operating in a box 55 which communicates with the jig chamber serves to pulsate the bed on the screen. Two middling traps 56 and 51 are located in the bottom of the trough intermediate the ends thereof. A screw conveyor 5I extends lengthwise along the bottom of the trough and is provided with a helix 59 on its lower portion and a helix 60 on its upper portion. The helix 59 is adapted to 'move aggregate which settles to the bottom of the trough following the jig upwardly to middling traps 56 and 51. The helix 50 is adapted to; move material settling in the upper portion of the trough Mineral aggregate is supplied to the lower end of the trough through a chute 68- located at a point such that the aggregate will tend to fallA into and not beyond the pulsating current inif the amount of dispensed ow 5| is provided at the shallow end of thev duced by the-jig. The separating medi/um '(an l aqueous suspension of galena, for example) is supplied to the deep end of the trough through a conduit '69 in-amount sufficient -to maintain the level of the contents of the trough approximately constant. Concentrates fall into and through .the

jig chamber and the screen into a concentrate with some of the separating medium or suspension. Middlings fall to the' bottom of the trough and are moved to the middling traps by the screw -70 trap 10. from which they are withdrawn together 3. In an apparatus of the character described of th trough together with some of the medium.

The function of the drag conveyor is to supplement the natural current in the shallow'end of the trough and to prevent crowding.

In the event that only three products are desired, the middling trap 56 may be omitted. Should more than three products be desired, additional product traps may be provided in the bottom of the trough.

I The separating apparatus illustrated in Fig. 2

is adapted to be substituted for the conical separator'shown in Fig. 1, when a multiple separation is desired.

It will bel understood that my invention is not limited to the use of a separating medium of suspended galena. Any appropriate solid may be substituted for galena. Thus, an aqueous suspension of hematite, barytes, pyrite, silica, clay, etc., or combinations thereof may be employed depending upon the respective densities of the minerals to be separated.

It will also be understood that the application of my invention is not limited to a case in which the specific 4gravity of the medium is intermediate the specific gravity of two minerals which are to be separated. By appropriate control, a plurality of minerals which are either heavier or ligher than the medium may be separated from each other for the reason that these minerals will rise or fall in the medium with' different velocities and thus become separated. I'he apparatus illustrated in Fig. 2 is particularly adapted to such practice.

1. In an apparatus of the character described,

Aa'tank having a bottom sloping toward one end of the tank, means for admitting material to be concentrated into the tank, a. concentrating cell in the sloping bottom of the tank and supporting a bed of the material with the top surfaces thereof extending in a plane substantially parallel with the bottom ofthe tank, means movable over the cell to effect removal of -the lighter material while the heavier material in said bed moves to the opposite side of the cell, and means for pulsating water through the bed in the cell to promote separation of the light and heavy materials.

2. In an apparatus of the character described a tank having a sloping bottom, a jig chamber opening into the bottom of the tank, means for pulsating the contents of the jig chamber, and

means disposed adjacent the sloping bottom of the tank and above the opening of the jig chamber into the tank for conveying settled material along the slope.v l 1 I L Vvariations in the density of material an elongated tank having a .bottom` sloping lengthwise of the tank, a jig chamberv opening into lthe bottom o f the tank, means for pulsating the contents of the jig chamber in'an upward Y direction, a screen in said jig chamber for retaining a bed of coarse solids, a conveyor for solids disposed lengthwise of the tank adjacent the sloping bottom and above the opening of the jig chamber into the tank formoving solids along the sloping bottom, means for introducing liquid into the tank, means for introducing solid particles to the tank, and means for withdrawing separated products from opposite end portions oi.' the tank.

4. Apparatus for effecting the separation of heterogeneous mixtures of relatively coarse solid yfragments in the presence of a heavy fluid which comprises a chamber, means -for introducing the heterogeneous mixture into the chamber, means for introducing the heavy fluid into the chamber,l means for vibrating the contents of the lower Iportion of the chamber, means for withdrawing relatively light coarse fragments from an 'upper portion of a chamber, -means for withdrawingA relatively coarse heavy fragments from af lower portion ofthe chamber, aconduit connected to the lower portion of the chamber, screening means near the inlet of the conduit to prevent the entrance of relatively coarse heavy fragments thereinto, a valvein said conduit and means for varying the setting of the valve in response to through said conduit.

5. Apparatus for eil'ecting the separation of heterogeneous mixtures of relatively coarse solid.

upper portion oi' the chamber, means for withdrawing relatively coarse heavy'fragments from a lower portion of the chamber, a conduit connected toa lower portion of the chamber, a screen disposed adjacent the inlet to Asaid conduit for preventing the entrance of relatively coarse fragments into the conduit, a valve disposed in said conduit, and means for varying the setting of the valve in response to variations inthe density of a mixture of heavy fluid and relatively ne fragments removed from the chamber through the Screen.

passing v CHARLES ERB wUENsoH. u

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