US2411288A - Froth flotation with simultaneous filtration and collection of froth - Google Patents

Description

Nov. 19, 1946. A. R. MORSE 2,411,233 FROTH FLOTATION WITHSIMULTANEOUS FILTRATION AND COLLECTION 0F EROTH .Filed uarh 26, 1945 f 2 sheets-sheet `1 JNVENTOA ALBEET EEY/VOPS HORSE A Trop/vn;

Nov. 19, 1946. A R, MORSE 2,411,288

FROTH FLOTATION WITH SIMULTAEOUS FILTRATION AND COLLECTION OF FROTH Filed March 2e, 1945 2 sheets-sheet `2 IN VEN TOR. ALBERT REYNOLDS /VOJESE ATTORNEYS Patented Nov. i9, 1946 i N l is 2,411,288 i i '2,411,288` s s rRoTH FLoTAfrIoN WITH SIMULTANE DUS FILTRATION F FROTH `rum COLLECTION l ab Albert Reynolds Morse, Shaker Heights, Ohio b ,l "Application March 26, 1345s7ena1no. 584,918

"I'his invention-relates to "a method and apparatusfor separating or concentrating the valuable constituents of mineral ores, i."e.`,"the` separation or concentration `of the morevaluable mineral or minerals `from the worthless part of the ore,` or gangue. More particularly the invention relates to the recovery of the valuable "minerals, metals or ,concentrates from flotation -cells. f f b The generalfobjects of `the invention are the 10 Vprovision of a method of separatingor concentrating the valuable minerals, 'metals and the l like (hereinafter collectivelyreferred to as concentrates') contained in` mineral ores at a decreased cost` and with increased efciency as compared to present methodsyand" the provision of a simple andeffective apparatus forfcarrying out `the method.` More specific objectslare the provision of an economical and eflicient method and an -apparatusforcarrying out the method '20` whereby concentrates of low moisture ,content can be recovered` from the froth produced by flotation cells." b b l The flotation method of'separating valuable minerals from ore is well known and `widely used; According to the ordinary practice, a watery mixture known as fpulp, containingthe ore towhich the proper `quantity and kind of .oil or other reagent has been added, is beaten s by an agitator or other means producing `a froth onthe top of .thelcell whichcontainslthe concentrates which it is sought torec'over. These `mineral*concentrates are `heavier thanwater, vbut are supported `by the froth above the liquid leveland `are ordinarily removed from thecell .35

by mechanically skimming the froth from the vcell. The froth containing the concentrates is diluted with water for convenience inhandling and then pumpedto asettling-t'ank orthickener,

andfinally to a filter where the concentrates are 40 separated from the Water and discharged into a inn;` ff According to the 'present invention, the" con `centrates are recovered vdirectly `from the yunthe upper sur- 145 diluted froth, preferablyfrom b face of the flotation cell by a downwardly facing surface disposed in contactfwith the froth,

1 then` Athe surfaceis removedfrom `the froth,

carrying with `-it `the concentrates, which are thereafter dischargedfrom the surface directly into `a bin. Preferably `thesurface is "composed I `cfa suitable filter` material, suchas a permeable fabric. The surface` preferably,` is continuous, and ismoved through a path lsuch that each for* controlling 4the application of portionthereof is `moved across the topofthe `112 claims. (Cilaos-7184)@ 's 1 s i i aration eeumm jcontact Iwith fthe with. then 'away from the celllwhere accumulatedconcentrates areremoved,l and then across the cell again, and so on. f Iprefer to reduce `the pressure lbehind that portionf theillter in contact with i the froth and apply pressure `to the portion over the bin tofdischargefthe:concentrates therefrom. I'hat portion of 4,the filter in ,contact` withthe frothu continuously picks up concentrates'from the undilutedfroth,"the concentrates being continuously removed inthe region adjacentthe bin. Thus the mechanismjrequiied formechan` ymuy skmiming th 1118er cells is enmmated," the dilution of the concentrates byjwater isfdone away with, andthe necessity for pumpingthe diluted concentrates tothe thickener and filter `cbviated,` resulting jinv substantial decreases "in operating, installationand capital costs as compared to present practices." Furthermore, by controlling the liquid levelin the cell, "the filter element may be positioned in contact with the `ifroth Aat the level containing the greatest amount of concentrates, insuring" efficient operation. 'I'he froth is continuously renewed by the operation of the agitators `orthe like, and fresh pulp is suppliedto the cellin the usual manner.l s "The arrangement is preferably such` that ith'econcentrates are picked `up lcontinuously from the entire surface of the cell, wthereby insuring rapid and efficint operation'.` The method maybe carried out rapidly and economically by sturdy and compact apparatus which can be constructed at relatively low cost and which requires substantially less investment in equipmentfand mill `A preferred form of japparatus 'forcarrying `out -my methodis illustrated in thedrawings 'ini which Figure `1fis a vertical section through a flotation cell embodying my invention and show.- inga preferredform of iilterapparatus forre moving the concentrates from the cell, thefsection` being taken as indicated .by line I`i "of Figure 2t Figure 2 is a horizontal Sectional view takenalong Aline 2``2 of Figurebl: Figures 3,2 df and 5 are 'sectional details onan enlargeduscale show the construction theefi Figure 7 is a sectional detail `of the filter element` takenalong the line`1-1 of Figure 6; "and Figure 8 .is a detail illustrating a preferred form ofbvalve` `plate b b suction and pressure to the filter element. y

annees tained substantially constant by conventional float controls and valves, not shown. As is customary, the float controls can be adjusted to vary the pulp level to provide the optimum yield.

Upon operation of the impellers or agitators I8, a layer of froth carrying the concentratesand comprising enormous numbers of minute bubbles welding. An intake is Adisposed at one side of the tank near the bottom thereof, the pulp being introduced through this intake in the usual manner. The tailings may be discharged lthrough the 'outlet I2 disposed at the opposite To receive y 'the concentrates recovered from the cell, I prefslde of the tank from the intake I I.

erably provide an arcuatel or semi-annular bln vI3, complementary to the tank 5, and made up vof a bottom plate, I4, curved side Wallsv I5 and I6,

" Yand radial end walls I1. This arrangement lends itself to the useoi!` acontinuously rotated annular tllterjelement disposed overthe annulus made up of the'tank'fl and'bin I3.

In order to agitate the. pulpjand generate the is formed in the usual manner onv the top surface of the liquid pulp as indicated diagrammatically at 40. In order to remove the concentrates from the cell, I preferably employ a filter indicatedgenerally at 4| and shown best in Figures l, 6 and 7. 4'I'he filter is circular in form, is supported concentrically with tank 5 and bin I3, andV may comprise a circular disk 42 having a downwardly extending :cylindrical peripheral flange 43 and a similar cylindrical inner flange 44. lThe froth, agitators Il!` and '18d Aare provided within the tank 5. lThese maybe of any conventional "construction, and while I have shown two such 'agitatorsin thelpreferred embodiment, it will be Y understood`A that if `desired onlya single agitator v may be employedor more than two agitatorsmay i 'be used, `depending uponl the ,size and 'shape of the-cell, andthe materials being handled. ;While the agitators themselvesmay be of any conventional construction, they are preferably driven `by lmechanismsl such as shown in the drawings, ratherV than by the conventional overhead or vertical drive mechanisms. The agitators I8 and |8a and their respective driving4 mechanismsrare preferably identical;l accordingly only the driving mechanism for agitatorl ,will be described in detail. The same reference characters are applied to similar parts in both mechanisms. Preferably, agitator `|8 is,l rotated at a speed of, for

example, about 1800 R..P.` M. by a shaft!! which is supported in suitable bearings 20 in a housing 2| mounted lin tank 5 byfthe supportingY bracka ets 22. At its upper end the shaft |9-is provided 'with a beveled gear 23 which isvengaged by the beveled gear`24 mounted on the `horizontal shaft' 25.i The shaft 25 is carried in suitable bearings in the horizontalhousingmember 21 and by the l outboard bearing 28, and is driven by motor 29 through pulleys 30 and 30a and belt 3|.

It will be `noted that the shaft 25 passes through a packing or stumng box 32as it leaves the housing '21, and the housing 21 is provided with 'a lateral inlet`33. to permit air under pressure to be supplied to the interior of the housing positive pressure may be maintained within the housings 2| and121, maintaining the level ofI any Vliquid'that mightleak past the end member 35 into the housing 2| below the level of the lower bearing 20. Thus,ithe bearings and gears of the agitator drive are protected fromv possibility of damage by the abrasive pulp contained lin the tank 5. Also, if desired, air can be supplied to the tank throughtheconduit 3,4 and housings 21 and 2|, being discharged into the p'ulpat the lower end of the housing 2|.

The usual anti-turbulence grid 31 Visprovided at the customary level. The pulp level is mainthrough the conduit 34. Bythis means a slight outer flange 43 vhas a radius slightly greater than the radius of the outer wall 1 of the tank, while a circular disk 45 having a radius slightly less. than the radiusbf theinner Vwall 6 is secu1d to the lower edge'of the ange y44'. I'he annular spacev between the'ilange 43 and the .edgel of disk 4 5 is covered lwith filtering material, forexample, canvas or othersuitablefabric, 46 backed up by wire screen 41. The c1oth ,46 and screen 41 are spaced from the disk 42 and the'spaoe between the disk land the. screen is divldedrinto a plurality of segments by radially extending vertical partitions 46, the partitionsseparating the entire filter in effet'into separate filter elements to each of which suction and pressure maybe successively .'applicd.k y

This last result isk obtained by .providigfuie plate 45 with a plurality of ports or openings 43 through which suction or pressure may Vbeappliedntherebeing `one port` or opening 43 for each segmental filterelement. lhe plate `45 alsofunctions to mechanically support the entire lter for rotation about its vertical axis,the plate being, supportedon block 5| carried by asuitable bearing 52 `upon the pedestal 53. The entire assembly is rotated by the drive shaft 54, which is driven at relativelyslow speed, for example one ortwo revolutions per minute, by the motor 55 through suitable reduction. gearing (not shown) and bevf eled lgears 56 and-51. Y i

In order to'apply suction lto the l`filtery segments l whenvthey are disposed in contact with'the froth on `top 4ofthe flotation cell and; pressure to the segments whenthey are over the bin\.|3,rI'pref erably employ a valve mechanism such as the valve plate 60 `which is disposed immediately-beneath the plate 45 and in sealing contact .there--y with. The plate 6|lasshown particularly in IIiIgure 8 has an arcuate suction port 6| and an arcuate pressureport'62 which -are adapted to reg-r ister with ther openings inv theplate ,45. The suction port 6| Vis connected through the mani fold 63 to the conduit v64 leading toa vacuum pump, while the pressure port 62 is connected through the manifold 65 to the rconduit 66 leading to a blower or othersuitable source rof iluid underpressure. Ii' desired, sealing rings Bland 59a may be provided to reduce leakage between the valveplate 60 and plate45. l By this arrangement, each segmental filter ele"- ment is connected with thevacuum line as the rotation Vof the entire `filter brings each element successively over the flotation cell 5 with the filter cloth 46 in contact with the froth on the top of ythecell.` Each port 49 remains'in communica'.

tion with the vacuum line during the entire time that its associated segment 'is -in contact withthe froth and until such segment approaches the Y are heavier than water.

asians scraper 10. The suction preferably is maintained as long as practical after the segment leaves the froth in order to remove additional moisture from the concentrates. As each segment approaches `the scraper in its travel over the receiving bin I3, its associated port 49 passes over the solid portion 61 of the valve plate 60, shutting oli the suction connection momentarily, and then registers with the pressure port` 62. ,Thereaften each port 49 remains in communication with the pressure port 62, and thus Vwith the source of air Y under pressure, as its associated segment travels in its arcuate path over the remaining portion of "the arcuate bin I3. As each segment approaches the end of the bin the pressure is cut off `by the solid portion 88, and then the suction connection is restored as the segment again comes in contact with -the froth.

In operation, the suction, coupled with the well known tendency of the concentrate film to adl age, andat thesame time to sufficient `clearance,

here to any surface, even though 4the bubbles making up the froth are broken, causes the concentrates contained in the froth to adhere` to the underside of the iilter cloth in the form of a paste or slime in spite of the fact that the concentrates The layer or cake of concentrates builds up on the undersldemf the -cloth of each segment asthe segment travels around and over the flotation cell, and the concentrates are discharged into the bin I3 by the application of pressure to the interior of the segments when they are disposed above the bin. 'Ihe scraper plate 10 is preferably provided to assist in the removal of the concentrates from the underside of the filter member. This `may be mounted upon suitable support 1I` (see Figures l and 2) and is arranged at an angle as shown to scrape the concentrates from the underside of ,the filter cloth and into the bin.

'I'he action of the filter elements in `picking up the concentrates from the froth is shown diagrammatically in Figures 3 and 4. As indicated in Figure 3, with the` filter turning in a clockwise direction, the `cloth 46 is `substantially free lfrom concentnates when it passes over the radial wall 9 of the tank `5. As it travels alongincontact with the froth it accumulatesa layer 13 `of `concentrateswhich is initially very thin as shown in Figure 3. This layer gradually becomes thicker as the filter travels across the tank in contact` with the froth, attaining a substantially greater thickness, as shown in Figure 4, by the time the lter Velement leaves the froth and passes over the radial wall I0. The concentrates, which as compared to concentrates recovered by conventional methods', contain a relatively small percentage of water, are then blown and scraped from the cloth in its passage over the bin I3 so that the cloth is substantially free from concentrates when it again reaches the entry side of the tank. In these figures, the layer ofconcentrates is necessarily indicated diagrammatically, and the drawings are Anot intended to showy the relativeV thicknesses of the screen; the lter cloth and the layer; for the thickness of the layer ofconcentrates may vary` within reasonably wide limits, depending upon the speed of operation, tough# ness of the` bubble film, amount of suction, the nature of the materials being handled in the cell, the fiotationoils or reagents, and other factors.

Figures 3 and 4 with Figure 5 also illustrate a preferred'arrangement for preventing loss of the froth and overflowing of the flotation een. I'his is preferably accomplished by mounting a exible rubber ange member `1l on the radial 6 wall l and engaging the underside of the nlter cloth as shown in Figure 3.` A trough 1l is provided to catch any froth or liquid that may overflow the wall 9. At the exit sideof the cell, a similar flange, bent in the direction of move-` mentmay belemployed, or I may employ rolls 15 and 16 mounted in the tank adjacent `the radial wall I Il the roll 15 being arranged to engage the layer of concentrates on the underside ofthe filter cloth.` The two rolls together function to block the space between the top of the wall I Il and the` lfilter cloth against excessive leakto preventthe layer of concentrates being scraped as `by the top of the wall I0. Here again, a trough member; 11 ,isL providedto catch any leakage.

4Similar fiangemembersare provided on the arcuate wallsl 6 and 1, Figure 5 showing the arrangement .on the outer wall 1, which comprises a rubber ange member 1B mounted adjacent the upper part ofthe `Wall and adapted to slideably engage the depending portion 19 of the flange 43. For convenience in illustration, the liquid and froth are not shown in Figure 5r 'I'hetrough member 80 is provided to catch any leakage. A

similar flange member `8| mounted on the inner wall 6 `(see Figure l) engages the peripheral edge of the valve plate` l5.A 'I'he troughmember 82 is provided to catch any leakage that may occur along this wall. `IBy this arrangement, the filter member is substantiallysealed against vthe upper e are withdrawn through the ,discharge pipe I2.

Thebeaters or agitators I8 and la are driven by the motors 29 at customary speeds, for example 1800 R; P. M f This produces the desired froth 40 at the top ofthe cell. i 1 The liquid level and supply of fresh pulp is maintained `by1automatic regulators of known construction to `provide a constantly renewed froth of the desired density in contact with the filter cloth 46. The l i motor 55 is operated to rotate the, filter member slowly to bring successively the various filter segments into contact with the froth, carry them across the cell in contact with the froth and then move them away from the cell and overthe bin I3." 'I'hrough the valve mechanism, each segment is connected to the vacuum or suction line t while it isl over the flotation vcell and in contact ywith the froth and each segment is connected `with the source of pressure as it is over the binV I3 and approaching the scraper 10. Thus the minerals are gathered on the underside of the filter cloth as the segments pass `over the cell and discharged from the filter cloth by the action of the pressure and by the scraper 10 as the filter segments pass over the bin. `'I'he speed. of rotationof the filter is correlated with the density of the froth and theconcentration of valuable minerals therein-to obtain a coating or cake of concentrates of the vdesired thickness on the underside of the cloth. f The `thickness of the layer or cake may` vary within reasonablywide limits, but it should notbe so great that the layer will crackand fallback into the iiotation cell.

filter, for `the method and apparatus are preferably operated vto produce concentrates of exceptionally low moisture content'. rThe speed of o perationv of the' filter may correspondgenerally with the speedof operation of conventional cy-v lindrical filters, for example speeds offene or'two revolutions per minute maybe employed. A vac-V uumof from 1.7 to 20 inches of vmercury is preferably applied to the filter when thinpulps are'employed, and this may be'inc'reased to'from 20V to `25j` inches 'of mercury with denser pulps. Pressure' up toV 7 to-15 pounds per square inch may be aplied on the pressure side oifthe cycle to'fblow the'pulp offthe filter cloth intothe bin.

' From the foregoingv description --of afpreferred 'form ofv my invention, it will befseen that by my i method the usualfoperations of skimming the concentrates 'from the top of a flotation cell then diluting the concentrates With water and pump ing them to thickeners and fllters'where the water Y is removed and the concentrates recovered, to-

gether'with the various items of equipment necessary to-carry out these operatidns, are all; eliminated. Thus-my method effects a substantial saving in the investment required to recover concentrates from' flotation cells and operates to re- V'cover .concentrates from such cells with greater efficiency, lower moisture content and at lower costthan has heretofore been possible. My preferred' apparatus for carrying'out my method is relatively simple and'compact and can be manufactured Aand/operated at reasonable cost.' l

Various changes andi-modifications can be made in my invention both as to method and apparatus without departing from the spirit andscope there- .of.`y "Therefore, it isto be understood that the foregoing description of my method and appa- 'ratus is given by way of example and not limitation,v and Vthatmy patent is not` limited vtofthe preferred' form disclosed hereinor inany man- .nerlfother vthan by ythe scope ofA the appended Y claims.

.. Iclalm: 1.,The methodlof recovering" heavierthan water mineral concentrates from a concentrate-conytaining'froth produced `by va flotation cell, which thereafter removing the filter from the vfroth and applying gas under pressure lto the upper sideof the filter to discharge the concentrates therefrom.

i 2. The method of removing heavier than water mineral concentrates from a flotation cell wherein the concentrates are containedin froth at the topl ofr the cell, which comprises placing apermeable filter with its lower surface `in contact With` the froth at the top of the cell and above the level of the liquid therein, applying suction to the upper side of the filter thereby causing concentrates contained in the froth to adhere to the underside of the filter, thereafter removing` the upper eide ef the portion of the filter in tenerci with the froth thereby causing concentrates con- 2 tained in the froth to adhere to the underside ofthe filter, continuously removing the filter from 5 the froth and applying gas under pressure'toV thev upper side'oftlie portion thereof out of contact with the fr0-th te discharge the eencentratee therefrom. e

4. The method of removing heavier than water mineral concentrates from a flotation cell wherein the `concentrates are contained in froth atfthe ,i

, top ofthe cell, which comprises moving a continuous filter element in a path suchv that during a'portion of its travel its lower surface is lin conportion is out of contact with the froth, applying suction to the upper surface of that portion of the filter element in contact with the froth thereby `causing concentrates to accumulate on the lower surface in contact with the froth, the movement of the filter" element lcarrying the accumulated `conc'entrates away from the froth, andremoving the accumulated concentratesduring theportion of travel of the element in which 'the element is out of contact withthe froth."

5. Apparatus for lrecovering concentrates from a'flotation cell wherein the concentrates are ,contained in froth at the topL of the cell, comprising, in combination with the flotation cell, a round and positioned to have one portion disposed over the cell with its lower surface adapted to` contact with froth in said cell and another portion spaced away from the cell, means for applying'suction to froth whereby concentrates may be yaccumulated thereon, means for removing laccumulated concentrates froma portion of the 'filter' spaced away from the cell, and means for rotating said filteniwhereby concentrates may be continuously accumulated on said filter and continuously removedtherefrom.

T6. Apparatus for recovering concentrates from fa notation' cell wherein the `concentrates are contained in froth at the topof the cell, comprising,

in combination with the otatlon cell, a roun:i, l substantially plane filter of. greater larea than the cell mounted for rotation about a vertical axis and positioned to have one vportion disposed over 5U thecell with its lower surface adapted to contact 'with froth in said cell and another portion spaced away from'the cell, sealing means mounted'on the walls of thev cell and engaging the under surface of said-filter for preventing substantial overflow 5;, of froth and liquidfrorn said cell, lmeans for 'applying suction to the portion of the filterr adapted to contact the froth whereby concentrates may be` accumulated thereon, means for removing accu mulated concentrates from a portion of the filter 6U spaced away from the cell, and means for rotating said filter, whereby concentrates may be con'- tinuously accumulated on said filter andA continuously removed therefrom; H,

7. Apparatus for recovering concentratesfrom a flotation cell wherein the concentrates`VV are contained in froth at the top` ofthe cell, comprising, in combination ywith ,the flotation cell, a round filter` mounted for rotation about :a vertical axis and positioned to haveone portion disposed over the-cell with its lower surface adapted to contact with froth in said cell and another portion spaced away Vfrom the cell, sealing means mounted on thek walls ofthe cell and engagingthe'under surface of said iilterfor preventing substantial overflow of froth and liquid from saidcelLmeans for applytact with the froth in the cell and durngranother' filter mounted for rotation about a vertical'axis Y the portion of the filter adapted to contactQthe contact the froth whereby concentrates may be accumulated thereon, means for applying pressure to a portion of the lter spaced away from the celi to remove accumulated concentrates therefrom, and means for rotating said filter, whereby concentrates may be continuously accumulated on` said filter and continuously removed therefrom.`

8. Apparatus for recovering concentrates from ores, comprising a flotation cell comprising a tank having means for creating a concentrate-containing froth on the surface of pulp within the tank, a bin, an annular iilter member mounted for rotation about a vertical axis, said filter member comprising an annularchamber having a lower surface of filter material, a portion of which is disposed over said tank and adapted to contact froth therein, while another portion is disposed over said bin, -radial partition members dividing said annular member into aV plurality of segmental filter elements, means for rotating said filter member to pass said segmental filter elements successively over said tank and said bin, andvalve means for successively connecting said filter elements to a source of suction when they are over said tank and to a source of pressure when they are over said bin.

9. Apparatus for recovering concentrates from ores, comprising a flotation cell comprising a tank having means for creating a concentrate containing froth on the surface of pulp within the tank, a bin, an annular lter member mounted for rotation about a vertical axis, said filter member comprising an annular chamber having a lower surface of filter material, a portion of which is disposed over said tankand adapted to contact froth'therein, while another portion is disposed oversaid bin, radial partition `members dividing said annular member into a plurality of segmental filter elements, means for rotating said .filter member to pass said segmental filter elements successively over said tank and said bin, and valve means for successively connecting said filter elements to a source of suction when they are over said tank. e l

10. Apparatus for recovering concentrates from ores, comprising a flotation cell comprising an arcuate tank having means for creating a concentrate containing froth on the surface of pulp within the tank,f a bin, an annular filter member concentric with said tank and mounted for rotation about a central vertical axis, said lter member comprising an annular chamber Vhaving a lower. surface of filter material, a portion of which is ydisposed over said tank and adapted to contact froth therein, `while another portion is disposed over said bin, radial partition members dividing said annular member into a plurality of segmental filter elements, means for rotating said filter member to pass said segmental filter ele-` ments successively over said tank and said bin, valve means for successively connecting said illter elements to a source of suction when they are over said tank `whereby concentrates are accumulated thereon as said elements pass over said tank, and means for removing said concentrates from said elements and discharging said concentrates into said bin. c 11. Apparatus for recovering concentrates from ores, comprising a flotation cell comprising an arcuate tank having means for` creating a concentrate containing froth on the surface of pulp within the tank, said tank extending for approximately 180` of arc, an arcuate bin concentric with the tank and extending for the remainder of the circular arc of the tank, an annular filter member concentric with said tank and bin and mounted for rotation about a central vertical axis, said illter member comprising an annular'V chamber having a lower surface of filter material, a portion of which is disposed over said tank and adapted to contact froth therein, while the remainder is disposed over said bin, radial partition members dividing said annular member into a plurality of segmental lter elements, means for` rotating said filter member to pass said segmental iilter elements successively over said. tank and said bin, and valve means-for successively connecting said filter elements to a source of suction when they are over said tank and to a source of pressure when they are over said bin. l c e 12. In combination with a flotation cell having means for creating a froth containing heavier ,Y than water mineral concentrates on the surface of the pulp within the cell, apparatus for recovering said concentrates from said froth comprising a rotatably mounted round iilter positioned to have one portion disposed with its lower surfacel adapted to contact undiluted froth, and another portion spaced away fromthe froth, :means for applying suction to the portion of the filter adapted to contact the `froth whereby concentrates 'may be accumulated on the under surface thereof, means for applying gas pressure to a portion of the filter spaced away from the froth to remove accumulated concentrates therefrom. and means for rotating said'filter, whereby concentrates may be continuously accumulated on said lter and continuously removed therefrom.V

ALBERT REYNOLDS MORSE.

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