US2202484A - Flotation apparatus - Google Patents

Description

May 28, 1940.- 'A. B. EMERY FLoTx-Iou APPARATUS Filed Des'.4 17, 1938 6 Sheets-Sheet l ATTORNEYS 6 Sheets-Sheet 2 ,jg f7 A. B, EMERY FLOTATION APPARATUS Filed Dec.. 17, 1938 l May 28, 1940.

INVENTOR z/gaszw wey ATTORNEYS May 28, 1940. A. B. EMERY FLOT ATION APPARATUS 6 Sheets-Sheet 5 Filed nec. 17, 1958 INVENToR l Aqyl/Jfw' 3. "fmevy BY 13M. Dm, www." y 914.,.1..

ATTORNEYS May 28, 1940- A. s. EMERY FLOTTION APPARATUS Filed Dec; 17, 1938 6 Sheets-Sheet 4 I BY 'Pl' I D.....-.. MN] 91....4

ATTORNEYS May 28, 1940.

A.' B. EMERY FLOTATION APPARATUS Filed Dec.' 17, 1938 e sheets-sheet 5 |NvENToR /lqyaams 5.522760/ PW DM. MWL. Qa ELM@ A'TToRNEY May 28, 1940. A. B. EMERY 2,202,484

FLOTATION APPARATUS Y Filed Dec. 17, 1958 6 Sheets-Sheet 6 Patented May 2s, 1940 UNITED STATES FLOTATION APPARATUS Augustus Bachelder Emery, Messina, Transvaal, Union -of South- JAfrica, assignor to Messina (Transvaal) Development Company, Limited, a corporation of Great Britain Application December 17, 1938,' Serial No. 246,261 13 Claims. (Cl. 209-170) This invention relates to the concentration of ores, and has for its principal object the provision of a new and improved apparatus for the concentration of ores by flotation.

ll Customary methods of concentrating ores by flotation involve the fundamental feature ofA producing a froth possessing selective attraction or preference for the metalliferous particles of an ore pulp in cntradistinction to the gangue particles thereof. For the formation of the froth, air or other appropriate gas is essential and commonly such air is provided by-agitation or aeration or by a combination of aeration and agitation of the ore pulp, or, as described in my 15 Patent No. 1,599,561', dated September 14, 1926,

by causing an ore pulpY containing an appropriate flotation agent to impinge, in the presence of air or other appropriate gas, against a bailling surface or the surface of a body of the pulp with suilcient violence effectively to break up the ore pulp streams and thereby form a mineral-bearing froth. The mineral-bearing froth formed as described in my above-mentioned patent is trapped beneath g5 the surface of the main body of the ore pulp and is recovered from a relatively quiescent zone of the main body of ore pulp. Preferably the ore pulp is circulated within an appropriate receptacle, in the course of which circulation the ore pulp is elevated to a height above the normal operating ore pulp level vin the receptacle and discharged back intov the receptacle where4 it is through the vessel. The circulation of the ore pulp in each cell of the apparatus is carried out in the manner which characterizes my abovedescribed method of flotation, that is, with the elevation of the ore pulp, preferably pneumatically, to a height above the normal operating ore pulp level in the V'receptacle, then the re-direction of this o re pulp outwardly and downwardly against a baiiling surface and against the ore pulp not so elevated with suilicient violence toform a mineral-bearing froth.

The elongated pulp receptacle of the invention is divided into a plurality of intercpmmunicating cells by one or more divider plates mounted transversely of the receptacle. In vmy preferred o apparatus, at least two spaced vertical ballles are mounted in each cell extending longitudinally thereof. 'I'he vertical bafes extend downwardly from a point slightly abovey the nornal pulp level in the cell almost to the bottom of the cell. An elongated air header is positioned in each cell between the vertical bailles and extends downwardly into the cell to point substantially below the normal pulp level in the receptacle.

One of the features of my improved apparatus is the provision of what I term a stream-lined path for the circulation of the ore pulp, so as to avoid any abrupt changes of direction of flow of the pulp. Where such abrupt changes occur, or where the pulp cell is so shaped that eddy currents are set up, there is a tendency for the solids to settle out of the pulp and deposit in` the bottom` part of the cells. Such settling out of solids causes irregularities in, or blocks, the free circulation of the pulp, resulting eventually in unsatisfactory operation of thecell.

'Ihis stream-lined path preferably is contoured and dimensioned as regards cross section area in a manner gradually but not abruptly to increase the velocity of the pulp at those places where there would otherwise be. a tendency for the solids to settle out and thus block the free flow of and upset the even distribution of sands in the pulp.

As an example of such stream-lining of the path of. pulp circulation in the new apparatus, the'junction between the bottom wall and the upwardly sloping side walls of the pulp receptacle are curved concavely from within the receptacle,

and the lower edges of the vertical bailles, which are positioned in the receptacle substantially vertically above said curved junctions, are curved correspondingly therewith to provide a passage free of abrupt changes in direction for the flow of pulp from the spaces between the vertical ballles and the side walls of the receptacle' to the pulp at or near the lowest point of the cell,v A

vfar apart"v (about'v'V to 9" center to center) 'that comparatively dead spaces of pulp 'are left between the air pipe openings, and consequently the eciency .of the cell is impaired because the mixing-of bubbles clair with the pulp is not uniform. Uneven mixing of air and pulp results in an uneven lifting forcein the air-lift, uneven very closely together.

froth flotation of the mineral contents of the pulp, and settling out of solids in those spaces between the air pipe openings where the pulp is less aerated and agitated.

When the pulp contains relatively coarse sands, or when the pulp is one from which the sands settle out rapidly, any opportunity for solids to settle out in the machine results in gradually building up sands in the pulp passageways and thus choking operation of the machine. This necessitates special hand or excessive high-pressure air agitation to free the chokes, or, al-

ternatively, a very much larger amount of compressed air must be used continuously. Excess air thus usednot only wastes power, but also causes a too rapid 0*'erflow of froth, making close regulation of the richness ofthe froth impossible.

In my machine the compressed air is discharged from the header through pipe openings spaced In order to secure adequately close spacing, the pipes are made small in diameter, and they are made short in length to reduce power losses due to friction, to increase their rigidity and to reduce the cost of renewals.

In order to employ the short pipes eifectively, the

intake ends are iixed into an air header positioned considerably below the pulp level instead of, as in other machines, above this level.

A further provision also has been made to insure uniform aeration of the pulp. In those machines in which unequal amounts of air are introduced into the pulp from each pipe opening, there is a tendency for pulp of greater density to accumulate at the openings of the pipes discharging the lesser amount of air, due to the reduced agitation and pulp flow in the vicinity of these pipe openings. This increases settling action at, and under, such openings, resulting eventually in the solids settling out around the openings and choking the discharge of air altogether.

In my machine equal distribution of air from each pipe opening is induced by throttling the air discharged from each pipe. 'Ihis is accomplished by reducing the area of the opening into the pipe at the intake end, so that the drop in air pressure due to the restricted intake is sufficient to prevent irregularities in pulp density at the discharge end of the pipes from affecting to a substantial extent the equality of ow of air from the-pipes. The restriction is made at the intake end so that pulp finding its Way into the air pipes may freely flow out again. f

The prevention of sand chokes over considerable areas at the bottom of the air lift is further assisted by varying the depths to which the discharge openings of the air pipes extend into the pulp. In my preferred apparatus air pipes discharge openings are arranged attwo or more l depths by employing air pipes of different lengths,-

and the depths of the discharge openings in the pulp are staggered in va manner such that the pipe openings deepest in the ore pulp have adtling Aaction of the pipe restrictions referred to above becomes less effective, but the uniform distribution of air is still maintained by the effect of the alternate comparatively deep and shallow pipe openings. Should the flow of air from the deep pipe openings become substantially reduced or fail, the ow of air from the flanking less deep pipe openings will be increased, and thus any tendency for chokes to form at the bottom of the air-lift in irregular areas will either b`e prevented altogether, or be restricted to a very small area, i. e. the area between any two air pipes.

A further feature of my new machine is the novel arrangement of means for collecting the submerged froth bubbles in the quiescent part of the pulp and the rapid discharge of the froth without moving mechanism, these means comprising baffles arranged inthe form of an in verted-funnel-shaped section into which the froth bubbles rise. The small end ofA theA funnelshaped section forms a narrow vertical columnar section at the top of which the froth overflows..

The height of the overflow of this narrow column is made adjustable so that the rate of froth over- `W, which rate determines the richness in mineral content of the concentrated ore product of the cell, can be regulated. 'I'he narrow `vertical froth column is made suiciently high, in any given case, to provide enough time, as the bubbles rise therethrough, for the froth to clean itself of such gangue material as may be inadvertently trapped in the rising bubbles. Increasing the height of 4this column reduces the velocity of upward travel of the bubbles and enables more thorough cleaning, with slower overow, of froth.

The large area of intake opening provided by the inverted funnel shaped froth collecting means assures that the maximum number of mineral-bearing bubbles are caught and forced to travel upwardly into the froth-cleaning column.

Still another novel feature of my preferred machine is the provision of substantially laterally positioned guide vanes cr baflles interposed in the path of circulation of the ore pulp in the cell and curved to impart a component of forward motion to the circulating pulp, thereby to insure ow of pulp longitudinally through the cells in series. These baffles thus provide means for propelling the pulp longitudinally through the long length of the receptacle making it unnecessary to give the bottom of the receptacle a slope in the direction of ow of pulp and making it possible to operate machines of indefinite length on one level oor.

The foregoing and other novel featuresd of the invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which- Fig. 1 is a cross-section, taken substantially along line I-i of Fig. 2, through a otation cell embodying features of the invention;

Fig. 2 is a longitudinal section taken substantially along line 2-2 of Fig. 1;

Fig. 3 is a cross-section through a pulp receptacle showing a divider plate in elevation;

Fig.4 is a plan view of an air-lift assembly employed inthe new cell;

' Fig. 5 is a cross-section through the air-lift taken substantially along line 5-5 of Fig. 4;

Fig. 6 is an enlarged cross-section through the lower end of the air header;

Fig. '7 is va longitudinal section through one end of a pulp receptacle showing details of construction in one cell; and

Fig. 8 is a cross-section through a plant installation of the new apparatus.

bil

The apparatus of the invention comprises an y elongated pulp receptacle I (Fig. '1) divided into a plurality of cells II by divider plates I2. The divider plates I2 extend from the top of the receptacle downwardly to a point somewhat below the normal level of pulp in the cell (indicated approximately by the broken line I3), leavingopenings I4 of large area for communication between the several cells below the normal level I3 of pulp in' the cell.

The receptacle III (Fig. 1) comprises a botto wall I5 and side walls I6, the lower portions of which slope upwardly and outwardly from the bottom walls. Mid-portions I1 of the side walls are arranged substantially vertically, and above these vertical portions the side walls slope inwardly and upwardly as at I8, and thence vertically as at I9.

The divider plates I2 which divide the receptacle into a plurality of intercommunicating cells are provided on each side with a pair of spaced guide brackets 26 between which an air-lift assembly is received. The air-lift assembly comprises a pair of spaced, vertically positioned baffles 2| extending from a point slightly above the normal level I3'of pulp in the cell downwardly to a point adjacent the bottom of the cell. A11 air header is positioned in the space between the vertical bailles 2| and extends from a point above the normal level of pulp in the cell downwardly into the pulp to a point substantially below the normal pulp level.

The air header comprises-an elongated, relatively `thin box-like structure having spaced, relatively deep side plates 23 held in proper spaced relation with respect to one another by spacers 24, and closed by a bottom closure 25, end closures 26, and a cover 21. The end closures 26 of the air header extend laterally outwardly substantially beyond the side plates 23 thereof and are formed with flanges 28. The vertical bailles 2| are riveted or otherwise fastened to and supported by the flanges 28 of the header end closures.

'I'he upper portions of the end closures extend laterally outwardly beyond even the vertical baffles 2| and are provided with flanges 29 for reception between the guide brackets 20 mounted on the divider plates I2. Since in the preferred form of the apparatus the flanges 29 extendrto a point below the upper edges of the vertical baflles 2| (in order to provide ample guiding and supporting area for the upper portion of the airlift assembly), brackets 30 are provided forsupporting the upper portions of the vertical bailles 2|.

The end closures 26 of the air header also ex-i tend downwardly below the side plates 23 about to the lower edges of the vertical baffles 2|, and

f' tacle with the air-lift assembly positioned in the cell as shown in Figure 1. The weight of the airlift assembly is carried by the end closures resting on the chair 32, and it is held in an upright position by the anges 29 received. between the guide brackets 20.

The upper portions 33 of the side plates 23 of the air 'header are curved outwardly and downwardly to provide curved deecting bales extending over and beyond the upper edges of the vertical ballles 2| and are supportedat their outer curved edges by outwardly extending projections 34 of the end closures 26.

The cover member 21 of the air header preferably comprises a pair of channel members 35 (which form a shallow frame for the header assembly) to which the outwardly curved portions 33 of the header side plates are secured. A ilat cover platel 36 spans and is secured to the channel members 35. f.

Means in the form of a'valve 31 connected 'to the cover plate 36 provide for introducing vair under pressure into the interior of the header. Eye-bolts 38 are secured to the channel members 35 to provide convenient means forremoving the air-lift assembly from the cell.

The bottom closure 25 of the air header 22 is preferably a strip, of shallow V`cross-section, suitably secured to the side plates 23 at their lower edges, as by welding. A large number of downwardly-projecting air discharge pipes or conduits 39 are threaded into suitably tapped holes arranged in two parallel longitudinal rows in the closure 25.

For purposes of collecting froth formed in the cell a pair of longitudinal vertical bales 40, each having its lower edge portion turned inwardly to form a lip 4I, are riveted or otherwise suitably secured to brackets 42 mounted on the divider plates I2 near the outer edges thereof. 'I'he baille 4I) is vertically positioned substantially parallel to the vertical baille 2| of the air-lift assembly between this baille and the vertical side wall I9 of the receptacle. The inclined lip 4| at the lower edge of the baille 46 cooperates with the ,inwardly sloping portion I8 of the side wall of the receptacle to forni inverted-funnel-shaped collecting means for the froth, and the vertical baille 40 itself cooperates with the upper vertical portion I9 of the side wall of the receptacle to form a froth collecting and cleaning column. The effective height of this'froth collecting and cleaning column is made adjustable by the provision of a gate orweir 43 of adjustable height. The gate 43 comprises one or more plates 44 removably mounted in brackets 45 secured to the outer edges of the divider plates I2. The elfec tive height of the froth collecting column between the gate 43 and the vertical baille 48 is determined by the height ofthe gate or weir 43, so

that by employing plates 44 of greater or lesserl width, or by employing more or less plates 44 of the same width, the effective height of the froth collecting column may be varied at will. 1 Splash boards 46 are mounted below the gate 43 to catch froth overflowing the gate from the froth collecting column.

As an alternative to theifroth collecting means specifically described above, I have investigated the possibility of omitting the inwardly slopingv portion I8 of theA side wall of the receptacle and instead carrying the side wall vertically upwardly from the vertical mid-portion I1 thereof, with the vertical baille 40 shifted outwardly in correspondence with such outward shift of the side wall of the receptacle, and with corresponding lengthening of the lip 4 I. Experiments prove the structure so modified to be substantially less effi- 4cientethan the structure shown in the drawings and described in conjunction therewith, however.

With the air-lift assembly in position as described in a cell of the receptacle, and with the cell lled `approximately to its normal level with a suitable ore pulp containing appropriate flotation reagents, the apparatus operates substantially as follows: Air under pressure is introduced into the header 22 through the valve 31 and is discharged -from the header through the discharge pipes 39. The air so discharged rises upwardly through the pulp, and by air-lift action induces upward circulation of the pulp, in the spaces between the side plates 23 of th'eheader and the vertical batlles 2|. The pulp attains considerable upward velocity as a result of the action of the air-lift, and upon ascending above the upper edges of the vertical baies 2| is deflected outwardly and downwardly by the curved portions 33 of the header side plates (which in effect are deiiecting baiiies) against the surface of the pulp lying outside the air-lift and against the vertical baiiles 40. A considerable amount of air is thusentrapped in the pulp with the attendant formation of a mineral bearing froth. The froth so formed is swept below the normal level of the pulp and into the relatively quiescent body of pulp underlying the lips 4| of the bailles 40. In this relatively quiescent body of pulp the froth rises and is collected in the funnel-shaped passage provided by the lip 4| and in inwardly sloping section I8 of the side wall of the receptacle, whereby it is directed into the vertical froth collecting column defined by the upper vertical sections |9 of the side walls of the receptable and the baffles 4I). The froth ascends this collecting column to a height determined by the height of the gate 43 and spills over the top thereof to the splash. board 46, from which it flows or is washed into suitable collecting launders.

As pointed out in my above-mentioned patent, the richness of the froth, that is, the degree to which it is free from gangue particles, is determined by the height of the gate 43. The higher the gate the greater is the length of time required for the froth to ascend` the froth column, and the greater, in consequence, is the opportunity for gangue particles to break loose from the froth and fall back into the main body of the pulp. In producing concentrates,` the top of the gate 43 will extend almost to the top of the cell, whereas in producing middlings the upper-edge of the gate 43 ordinarily will be considerably below the upper edge of the receptacle and may not be much above the splash board 46.

The ore pulp lying outside the vertical baiiles 2| and below the froth formed and collected as described above responds to 'theaction of the air lift by circulating downwardly toward the bottom of the receptacle, where it passes under the vertical baiiies 2| and into position for upward circulation through the air-lift. in order to provide a path of pulp circulation substantially free of abrupt changes in direction, the junctions 41 between the horizontal bottom wall 50 of the pulp receptacle and the side walls sloping upwardly and outwardly therefrom are curved concavely from within the receptacle. The lower edge portions 48. of the vertical bailles 2| (which are proxi mate to but overlie the'junctions 41) are bent outwardly and upwardly with a degree of curvature corresponding to that of the curved junctions 47. A curved passage 49 free of abrupt changes in direction thus is provided for the flow of pulp from outside the vertical baliles 2| into the space between them. The extreme edge portions 50 of the vertical bailes 2| lying beyond the curved portions 48 thereof, are bent inwardly toward the vertical portions of 4the bales and provide, in conjunction with the outwardly sloping side walls I6 of the receptacle, a funnel-shaped section for directing pulp easily into the curved passages 49.

The cu'rved passages 49 and the funnel-shaped approaches thereto provide a minimum of resistance to the passage of pulp from the spaces outside the vertical bailles 2| to the space between them, and in consequencev reduce materially the power required to operate the air-lift and maintain adequate pulp circulation. l

Some importance attaches to the depth of the passages 49. The precise depth of the passages will vary somewhat depending on the conditions under which the cell is operating, but in any event the. cross-sectional area of the passage (taken,

of courselongitudinally of the cell) should be 10 small .in proportion to the cross-sectional area oi the cell at points above the passage 49. In operation of the cell heavy sands tend to collect at the bottom and by making the cross-sectional area of the passages 49 relatively small the velocity of the circulating pulp passing through these passages is made relatively high; the tendency of heavy sands to settle thus is minimized.

4Further to relieve the tendency of heavy sands to settle and clog or choke the machines, the pipes or conduits 39 through which air is discharged from the header 22 into the pulp are so constructed and arranged as to provide for uniform and even distribution of the air introduced into the pulp. To this end the conduits 39 (Fig. 6) 25 are provided with intake openings 5| of reduced area where they are tted in to the bottom closure of the air header. Such reduction in the area of the intake opening 5| may be provided by bending the intake end of the conduits 39 in- 30 wardly (as shown in the drawing) or by otherwise partially plugging the intake end of these conduits. By thus reducing the intake-opening area of the conduits 39, discharge of air from the header is throttled somewhat so that accumulation of heavy sands in the vicinity of any discharge conduit or conduits does not materially affect the volume of air discharged therefrom. Such restriction in the conduits thus in effect anticipates accumulation of heavy sands, and 40 prevents such accumulation, should it occur, from being the primary cause of throttling and bringing about a reduction in the amount of air introduced into the pulp. More uniform distribution of air than has heretofore been possible through pulp in which sands may not be uniformly distributed thus is assured. 'I'he restriction 5| in the conduit 39 preferably is provided as shown at the intake end in order that sands working into the interior of the conduit may freely be depths into the pulp. Thus alternate pipes 39a 60 are relatively long and extend relatively deeply into the pulp. li'lanking these relatively long pipes 39a are relatively short pipes 39h and 39e which project less deeply into the pulp. If desired, the relatively short pipes 39h and 39e may 35 be all of the same length, thus providing for discharge of air at two depths in the pulp, but in my preferred apparatus one set of pipes 39h is made of intermediate length and another 39e is of still shorter length, so that discharge openings are provided at three dierent depths in the pulp. By thus providing for introduction of air into the pulp at a plurality of depths, improved uniformity of air distribution through the pulp is achieved, and heavy accumulation of sands at the are arranged in series throughout the length of the pulp receptacle I9. Ore pulp to be'treated is introduced into a feed chamber 53 (Fig. 7) at one end of the receptacle and passes thence through the cells in series to a' discharge chamber (not shown) at the other end of the receptacle. In order toassure movement of the pulp! longitudinally through the receptacle, a plurality of laterally-arranged propelling bailles 54 are riveted or otherwise secured to the vertical bailles 2l of the air-lift assembly. TheseA laterally arranged bailles are curved concavely from above and mounted in a manner such that a component of forward motion is imparted to pulp moving downwardly in the space between the vertical bailles 2| and the side walls of the receptacle.'-Thus positive longitudinal propulsion of pulp through the cells in Aseries is achieved, utilizing for this purpose the force provided by the air-lift, and avoiding the customary expedient of inclining the bottom wall of the pulp receptacle to secure forward flow of pulp. Provision of the propelling bailles 54 makes it possible to operate cells of indefinite length on a level oor.

The laterally arranged bailles 54 serve another purpose in that they arrest downward movement of circulating pulp in which froth has been entrapped, and so enhance the opportunity of the froth bubbles to separate from the pulp and rise upwardly in the vzone of relative quiescence beneath the froth collecting lip ll.

The number of propelling baies 54 required in any given installation, as well as their exact curvature, is best established by trial, and once ascertained does not usually require alteration thereafter. To a considerable extent, correction for excessive forward propulsion of the pulp by the baies 54 is automatically provided for by a reverse flow of the pulp through the lower half of the receptacle, made possible by the very large openings between the. cells below the divider plates l2. withdrawal of pulp that hasftraveied the 1ength of the receptacle is made from the discharge chamber (not shown) at the end thereof through the V'agency of any suitable pulp-levelregulator. A satisfactory pulp-level regulator is -a standard low pressure air-lift which elevates the pulp from the bottom of thedischarge chamber and over the top thereof. The supply` of air to the discharge air-lift in such a regulator is controlled by a oat resting on the surface of the pulp in and 8) are connected to valved inlets 56 provided -the discharge chamber. Any change in the pulp level above ,or below the level to be maintained `elevates or lowers the float to increase or decrease the supply of air to the discharge air-lift; and

- hence to increase or decrease the volume of tailings pumped from the chamber.

The air-lift assembly of the new apparatus 'as described above is removable as a unit from the cell for purposes of clea g or repair. Preparatory to such removal, fl kxible air lines 55 (Figs. '1

in the cover plate 35 of the air header. High pressure air from an air line 51 is admitted to the header 22 by opening the necessary valves, and the primary source of air to the header 22 from a main air line 53 is cut oif by closing the valve 31 mounted on the header and another valve 59 in the branch conduit 60 through which air passes from the main air line to the header. A flexible section 6I in the branch line between the valves 59 and 31 is removed, and the entire air lift assembly is removed bodily from the cell by a crane attaching to the eye-bolts 33. The high pressure air supplied to the`header from the line 51 serves to prevent the header from filling with pulp after closure of the valve 31 on the'header 'and disconnection of the exible section 6I of the main air supply line. 'I'he lines 55, being flexible, do not interfere with removal of the header from the cell, 'and after such removal may be disconnected.

It is apparent from the foregoing description of my new apparatus thateach cell is in'effect a pair of independently operable half cells. If

desired, operation of either half of the cell may` be discontinued by closing the air discharge con-- f duits 39 in the row along that half of the celllwhich it is desired to close down. Moreover, the l Atwo halves'of the cell may be made substantially completely independent in their operation by suitably closing the space between the bottomwall 25 of the air header between the two rows of discharge pipes 39 therein and the bottom wall I5 of the receptacle.. Such operation of only half of the cell or independent operation of both halves may be desirable in small installations, but in general operation of both halves of the cell as described above is preferable.

I claim:

1. Apparatus for concentrating ores by flotation comprising an elongated receptacle adapted 'to contain ore pulp, divider plates mounted transversely of the receptacle dividing the receptacle into a plurality of intercommunicating cells, a vertically disposed baille mounted in the 'cell and extending from a point slightly abovethe normal pulp level in the cell vto a point adjacent the bottom of the receptacle, and a second vertically disposed baille arranged substantially parallel to said rst-mentioned baille between said first-mentioned baille and a side wall of the receptacle and extending upwardly from a point slightly lbelow the normal pulp level in the cell, said second baille having a lip at its lower end turnedinwardly at an angle to the vertical toward said mst-mentioned baille, said lip serving to assist in collection of froth formed in the space between said two bailies.

2. Apparatus for concentrating ores by -otation 'comprising an elongated receptacle adapted to contain ore pulp, divider plates mounted transversely of the receptacle and extending from a point above'the normal level of pulp in the re.

ceptacle to a point therebelow but above the bottom of the receptacle, whereby the receptacle ris divided into" a plurality of cells communicating with each other adjacent the bottom of the" receptacleklne'ans for inducing circulation of ore pulp within each cell in a direction substantially at right angles to the direction of ow of the ore pulp through the receptacle, and laterally positioned bai'iiesinterposed in the path of pulp circulation in each cell and arranged to impart forward motion to the circulating pulp as said pulp vcirculates downwardly below the bottoms of the divider plates to insure i-low'of pulp longitudinally through the cells in series. y

3. Apparatus for concentrating ores by flotation comprising an elongated receptacle adapted to contain ore pulp, divider plates mounted transversely of the receptacle and extending from a point above the normal level of pulp in the renent of forward motion to the circulating pulp as said pulp circulates downwardly below the bottoms of the dividerplates to insure flow of pulp longitudinally through the cells in series.

4. Apparatus for concentrating ores by otation comprising an elongated receptacle adapted to contain ore pulp, divider plates mounted transversely of the receptacle dividing the receptacle into a plurality of intercommunicating cells, a pair of spaced, vertically disposed bailies mounted in each cell longitudinally of the receptacle,

means for circulating pulp upwardly in the space' between said baiiles and downwardly in the spaces between each of said baies and the side walls of the receptacle, and laterally arranged baiiies mounted in the spaces between said vertical bailles and the side walls of the receptacle and curved concavely from above in a manner to impart a component of forward motionto pulp moving downwardly in said spaces.

5. In a flotation cell of -the character described, a receptacle adapted to contain ore pulp, a pair of spaced, vertical bailies mounted in said receptacle, an elongated air header of relatively large cross sectional area mounted in the space between said bailles and extending to a point substantially below the normal level of pulp in the cell, and a plurality of short, closely spaced air discharge conduits of small diameter to permit close spacing mounted in the lower portion of said header and extending downwardly therefrom to a point adjacent the bottom of the receptacle.

6. An air header for use in oation apparatus of the character described comprising a thin box-like structure of relatively large cross section area having spaced, substantiallyy parallelA side walls, end walls, bottom wall and cover, means for introducing air under pressure into said header, and a row of short, closely spaced airdischarge conduits of small'diameter to permit close spacing communicating ywith the interiorof said header through the bottom wall thereof and extending downwardly therefrom.

7. An air header for use in oation apparatus of the character described comprising a thin boxlike structure having spaced, substantially parallel side walls, end walls, bottom wall and cover, means for introducing air under pressure into said header, and a row of small, closely spaced air discharge conduits communicating with the interi Jr of said header through the bottom wall thereof and extending downwardly therefrom, said airdischarge conduits having restricted intake openings adjacent. their points of communication with the interior of the header.

8. An air header for use in otation' apparatus of -the character described comprising a thin boxlike structure having spaced, substantially parallel side walls, end walls, bottom wall and cover,.

means for introducing air under pressure into said header, and a row of small, closely spaced air discharge conduits communicating with the interior of said header through the bottom wall thereof and extending downwardly therefrom, alternate air discharge conduits being longer than and extending downwardly toa point below the ends of the intervening air discharge conduits. i

9. An air header for use in flotation apparatus of the character described comprising a pair of spaced side wall plates, and end, bottom and top closure members enclosing the space between said side wall plates, the upper edge portion of said side wall. plates being curved outwardly and downwardly.

10. An air header for use in a flotation apparatus of the character described comprising a relatively shallow frame, a cover plate over said frame, a pair of relatively deep, relatively closely spaced side wallV plates mounted substantially parallel to each other and curved outwardly and downwardly at their upper edge portions, said side wall plates being secured adjacent their upper curved edges to said frame, and end and bottom closures enclosing the space between said side wall plates.

11. An air lift assembly for use in notation apparatus of the character described, comprising spaced, substantially parallel air header `side plates, a bottom closure and a cover secured to said side plates adjacent the upper and lower edges thereof, end closures secured to said side plates at each end thereof and projecting laterally a substantial distance beyond the outer surfaces of said side plates, and baille plates secured to said end closures adjacent their outer edges andsupported thereby in spaced, substantially parallel relation with the header side plates. 4

12. An air lift assembly for use in flotation apparatus of the character described, comprising spaced substantially parallel air header side plates, a bottom closure and a cover secured to said side plates adjacent the upper and lower edges thereof and projecting laterally a substantial distance beyond the outer surfaces of said side plates, balile plates secured to said end Y closures adjacent their outer edges and supported thereby in spaced, substantially parallel relation with the header 'side plates, and substantially laterally-arranged propelling baille members curved concavely from above secured to the outer surfaces of said baiile plates.

13. An air lift assembly for use in notation apparatus of the character described, comprising spaced substantially parallel air header side plates, a bottom closure secured to said side plates adjacent the bottom thereof, end closures secured to said side plates at each end'thereof and pro- *jecting laterally a substantial distance beyond the outer surfaces o f said side plates,` baille plates secured to said end closures adjacent their outer edges and supported thereby in spaced, substantially, parallel relation with said side plates, said side plates at their upper edge portions being curved outwardly over and downwardly beyond said baille plates, and a cover secured to said side plates adjacent their upper curved edges.

' .AUGUSTUS BACHELDER EMERY.

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