US2944802A - Froth flotation and aeration apparatus - Google Patents

Description

July 12, 1960 A. c. DAMAN 2,94 ,8

FROTH FLQTATION AND AERATIONAPPARATUS Filed Feb. 16, 1955 2 Sheets-Sheet 1 i m INVENTOR. V fli fig gg ARTHUR C. DAMAN FIG. 5.

ATTO PNEYS July 12, 1960 A. c. DAMAN FROTH FLOTATION AND AERATION APPARATUS Filed Feb. 16, 1955 2 Sheets-Sheet 2 Fla. 4-.

N V EN TOR.

4% a 72 6.nL 5 1 2 7h 82 M :V v 4 MW 2 ,M g/ 4 United Sta s 2,944,802 nRoTH FLOTATION AND .AERATION rr IUS Arthur C. Damon, Denver, (3010., assignor, by 'm esne assignments, to Denver Equipment Company, Denver, 'Colm,acorporatinnoficoloradq a I Filed Feb. .1 6,.1955, Sen No, 488,523 s Claims. (c1. zen-s1 invention relates to aeration apparafus 'forfiotaition processesand more particularly relates to aeration features embodied in'a'frotl'l flotation eellY i ln'froth flotation. treatments'lt p v quantities or air; or other aerating gas: are introdueed 'into'aiidmixed with thecirculating pulp in a flotationfcellfso"as"to elevate filmed particlesfwhich will carry to the surfaceandcol lec t in a froth which can be removed as a concentrate by overflow or otherwise. Unless suitably controlled,

large bubbles tend to form in suchopera'tioiiswlii'ch breakand release mineral before reaching'the frotlijbed. In addition, large bubbles do not" distribute 'unirsrmw throughout the pulp ,body and therefore are not aneflieient means for elevating 'the'coat'ed' or filmed particles. It isadobjctof the present invention tshprevide simple, durable, and efficient apparatus for dispers'iri'g an aerating gas throughout a circulating pulp and fOrreicirculating aerated pulp through its zone ofprimary mixing 1 'Another"object of this invention is to provide simple, durable" and eflicient apparatus for controlling uieuow [of circulating pulp and aerating gasin a mixing zone so to accelerate the rate and amount of intermixture under centrifugal influence. Other objects reside in novel details of construction and novel combinations and arrangements of partsas will be more fully described in the courseof the following description. 7

f The practice of the present invention will be best under stood by reference to the accompanying drawing illustrating typical embodiments and installations; 'In the drawings, in the several views of' which like parts bear similar reference numerals: f

Fig; l is a vertical section through a single cell. of a multirc ell flotation machine utilizing features of this invention;

. h A V v a cell to the next in, series. A cove-type bottom linear-14 in the cell assists the sweep of the impeller in directing settled solids into the passages 13.

' Circulation or pulp in the cell is inducedby an nuns iihit' including a rotary hollow shaft .15 journalled in bearings? 16and driven by a suitable prime mover (not shown). A rotary impeller member17 is carried at the lower end ofthe shaft and" in the form shown is the stasaardroenversus A'impeller having a'hub portion 1'8 "fitting the shaft, a. dished bottom portion 19, blades 20 spaced from the'hub, and disposed in radial arrangement' on the upper surface, while pumping vanes 21 are provided on" the 'under surface of said impeller.

- The impelleris substantially enclosed by a cover member 23"ha'ving' a series of'depen'ding radial blades-24 forming an enclosure forthe impeller. A hollow column 25 extends upwardly 'from'cover'lfq andeonnects'with the'housing'f of beaii'ng structure 16 to provide a rigid support for covet-'23 which. has its under: surface substandaily Iparallelwith and in close proximity to the top sur- 'face ofibl'ades '20. This sp'acing may be variedby inse'rtjionofone'or moii'espacer rings 26 betweenthe bottom flange l6fof the bearing assembly and the topfflange '27fof7column 25', and provides for varying the mixing and pumping function of blades 20. J i This-type of flotation; cell is factory-built for use of either atmospheric air 'or gas'under pressure, such as compressedair' for example; To this end, a plurality of threaded-openings 28 are provided adjacent the upper closed end of column 25. 'If air under pressure is to be provided, all? the openings" except one will, be closed. by suitable plugs 29 and a line 30 connected with a suitable source of gas under pressure (not shown) delivers gas into column 25 and thence through openings (not shown) into""th'e' hollow shaft 15. Otherwise, all the plugs 29 are removed permitting substantial intake of. atmospheric air through column 25.

Pulp from the feed compartment F entersatubular 17 and this pulp mixeswith the feed through conduit '32 before descent onto the impeller surfaces. One .Or a

plurality" of upper'opem'ngs 38 may admit a recirculating middlings-preduct from the upper portion of thecell for mixing'iricol'umn' 25. Air'admitted through open- O Fig. '3 is a section through the. hollow column taken along the line 3. 3, Fig. 1; v j Big. 4 is a top plan view of a modified impeller and bottom. liner arrangement for use in a cell of the type shown in Fig. 1 and corresponding to a tti'on taken along the line 44 Fig} '5;

Fig. 5 is a fragmentary section taken approximately along the linev 5-5, Fig. 4, showing amodified form of pulp distributor and'aerating arrangement; and I developed sec- @Fig. 6, is a sectional view ofa modificationof a pulp aa'esu 0 represents an intermediate cell of-a mult-icell J distributor housing foruse in an aerator of thetype rriachine i of the well known Denver Sub A? type and receives-pulp from -a preceding: feed compartment F and .dis'glrargesinto a following feed compartmentF'. An d tab s W v r sw 2,- la es e aaitli i each feed. compartment supplemented by lower passage 13' permitting the circulation of coarse sands fromone i'ngs 28 ordischarged by line30 is drawn through column 25' and through'hollow shaft 15 by the pumping action of'impeller 17. The bottom of shaft 15 preferably is open ended asindicated at 36 so the descending'gas may discharg'efunder theimpeller and the pulp moved bythe "top and bottom surfaces of the impeller is aerated in such movement. Additional aerating gasmay be deliveited under impeller 17 by'a nozzle 35. "The features thus far described, except in the're'spects hereinafter noted; are more orless standard in the"Den ve'r S'ub A machine. In order to provide a morewid'espread distribution of the aeratinggas throughout the pulp bodyand a more intense recirculation,'*a pulp distributor'is mounted inside the hollow column 25'adjacent its base. In the-form'shown in Fig; lthedistributor comprisesa tubular member 40 mounted for conjoint rotation with shaft'1'5. f 1 In this: arrangemenhsthe. tubular member issupported byaseries of upper pumping vanes 41 and arseries ofslower pumping vanes 42. The-lower end; oftubularmember 40' widens and terminates in a fiangedrport'ion fimhich inthis -forinabuts-againstoris .slottedtofitonrthe inner ?atented .July

peller in non-radial arrangement.

the aerated pulp traveling along the inner passage 45 may be directed underneath the impeller 17 for mixing with other pulp being moved by vanes 21 and finally strikes .vanes v24 depending from cover member 23 to receive additional mixing from the resulting shearing effect.

Larger pumping vanes 47 are located on the outer wall of tube 49 within passage 46 adjacent feed conduit 32 the lower end of passage 45 and each stream of pulp passing onto the impeller is activated by, the venturi effect of the passage with the result that a high degree of mixing and downward motion is obtained in the converging movement of the streams under centrifugal influence of the impeller.

The operation performed in cell C is as follows: Pulp from a preceding cell overflows weir 12 of compartment F and other pulp enters said compartment through opening 13 at its bottom. Pulp flows from the compartment F into a feed conduit 32, the entrance of which is substantially restricted as indicated at 50 (Fig. 1), and preferably this conduit has a lengthwise ridge 51 as shown in Fig. 2 which divides the flow of pulp into separated streams directed toward the axis of rotation of the im- A more effective distribution and better mixing with the aerating gas occurs as a result of this arrangement. The aerating gas is supplied either through a conduit in the manner previously described or through the series of openings 28 in the top of column 25 above the liquid level of the cell which is indicated by the dash line L in Fig. 1. Some of the air enters the hollow shaft through suitable openings aligned with the intake (not shown) while the remainder is drawn downwardly through column 25 under the pumping influence of impeller 19 and its associated structure. When the descending air reaches the top of tubular member 40, it divides with one portion flowing through passage 45 while the remainder travels through passage 46.

Pulp entering through feed conduit 32 and one or more of the recirculating openings 33 mixes with the descending air stream in passage 46 first by entrainment and then by the beating effect of blades 47. If any back pressure develops which causes the level of pulp within column 25 to rise above the top of member 40, the pulp flow will distribute with the air and ultimately pass to the impeller through passages 45 and 46. The lower end of tubular member 40 is shaped with reference to the associated imlpeller structure so as to provide a venturi effect on pulp flowing through both of the passages prior to its ultimate direction by the extended portion 43. Movement of pulp in said passages is also accelerated to a considerable degree by the series of blades 41, 42 and 47 which due to .their shape effect a substantial pumping action in addition to the beating or impact influence exerted on the pulp. The shaping of the impeller 19 and associated cover .23 direct the separated streams passing over and under extended portion 43 into converging relation, and the blades 20 of the impeller exert a beating effect on the pulp as well as impelling it under centrifugal influence. Preferably the impeller will have bottom openings 44,

and gas outlets 36 will be provided at the bottom of shaft ing a fine distribution of the aerating gas throughout the body of pulp beyond the blades 24.

Another novel feature of the present development is the housing arrangement shown in Fig. 6. In this modification the housing 60 will have one or more openings, here shown as four, in which port members 33a are fitted. A feed conduit similar to the conduit 32 of Fig. l and of a diameter to fit the opening of one-port 33a will provide the main pulp feed to the unit while one or more of the remaining openings may be utilized for recirculation of pulp. if too much recirculation is provided by the entire group of openings, one or more of same may be plugged as required.

As shown in Fig. 6, a pulp distributor 40a, similar in shape to the distributor 40 of Fig. 1, is mounted on a spider 61 and supported as a stationary member within housing 60. Other details of this distributor arrangement are shown in Fig. 5 and will be described hereinafter. I have found that with the non-radial port arrangement shown in Fig. 6, a superior mixing action is attained over any radial arrangement of the type heretofore employed in the art. Preferably, this arrangement will provide a flow into the housing directed substantially tangential to the impeller rotation as indicated by the non-radial discharge 'will provide better mixing than is derived from the radial intake arrangement. The arrangement of Fig. 6 is utilized in the flotation cell whenever it is preferable to have the distributor mounted as a stationary member instead ofrotating with the shaft as in Fig. 1.

Fig. 4 illustrates a modified form of bottom cell liner and impeller arrangement which is particularly effective in handling pulps containing a considerable amount of coarse material. In the preferred arrangement, a liner assembly is formed of a plurality of liner segments 63, each of which has-an inclined forward surface supporting a series of upstanding projections or vanes 64 arranged at intervals in an arcua-te course. Rearwardly of the inclined surface, the segment has a flat portion terminating in an upstanding rim 65, the inner or forward face of which preferably is inclined as shown in Fig. 5. The series of segments are arranged to form a substantially annular liner, the vane and rim portions of which are in the horizontal plane of the impeller, and its associated cover member and the vanes 64 are in proximity to but spaced from the depending vanes 24 of the cover member to provide an additional shearing effect on the pulp moving outwardly from the impeller under centrifugal influence, and following this final shearing, the pulp encounters the inclined 65 to provide an elevating component to all of the pulp.

This arrangement serves to throw all solids of the pulp into suspension whether they are of freely settling character or otherwise, and a high degree of mixing and dispersion of gas through the pulp and in contact with the particles results from this control. As shown in Fig. 4, the segmental arrangement permits omission of segments immediately adjacent to the inlet and outlet of the cell with the result that coarse material can be moved rapidly through the cell to its point of ultimate discharge. When more suspension of particles is required, or a longer flotation time, the segments may be arranged in a complete annulus and will thereby create the upcast condition throughout the entire area of the cell.

For some types of operations, it will be desirable to provide even more aeration than can be conveniently handled through the hollow column and hollow shaft. To this end, the cover member 23 may be apertured for connection of pipes 67 Fig. 5 which extend upwardly through the cell and may be connected with the gas header of the machine or provided with an open end above the pulp level of the cell for atmospheric air intake. With attests such art-arrangement, it is possible to feed reagent through the pipes:- 67 when additional reagent miJdng by- 'the-impelleri's -required. 1v W i 'As shown in Fig. 5, the-stationary pulpdi'stributor 40a previously-described is mounted-on a hollow-column has been shown in Fig. .in which a small rib or projection extends from a pointadjaccnt the shaft to'a second point near the periphery of the impellerzand-widens subs stantially'at said second point:to..provide a 'vanexzla of substantial vertical extent. extending radially from the second. point to the periphery This arrangement produces a pumping effect on pulp adjacent the bottom of .the cell and particularly-any settled solids of the pulp which throws them; outwardly into the, stream of material moving toward rim 65 providing substantial contact, with the aerating gas: and -vreceiving;-the final elevating effect necessary to carry such solids into; suspension; 2

' The structural arrangements hereinbefore-. described are well suited for use in-a novel type of flotation process. I have discovered that when an 'ore'pulpcontaining a substantial quantity of slime sizes, a substantial portion of which are the valuable constituent of thetreatment, is treated by the usual froth flotation procedure, the slime sizes tend to float in volume in the first cellsofthe series but are greatly impeded in such action by thev scouring effect of coarser particles As. a consequence of, this activity, a flotation of both the slimes and the coarse sizes is relativelyinefficient, and this condition persists even when the pulp is passed progressively through, a, considerable number of cells. in series. However, by regulating. the rate. of flow. of .the respective constituents in a size' segregating action it is possible to first effect a flotation in, which the concentrate is predominantly intheslimesizes, following which the slime-depleted pulp issubjected to a treatment in a second group of cells under a control which is directed to the flotation-r of the coarse sizes. andformsa concentrate which is predominantly in thecoarse size range. The total concentration attained through this procedure is substantially greater than a conventional treatment of the same ore through a corresponding number of cells.

' In order to attain the necessarycontrol, the. passages :13' i'n the first group of cells will be of substan'ti'allylar'ge diameter to permit a rapid discharge of coarse sizes, and preferably, the bottom liner arrangement shown, inFig. 4 also will be utilized'to accelerate the rate of coarse product'discharge. At the same time-the overflowweir setting in', the this .group of cells will be maintained sufliciently high todelaythedischarge .oflsuspended solids so that the overall effect of this control is to substantially increase the proportion of coarsesolids to slirnes in the discharge from each cell In addition, it .will berpreferable to run the impeller at slow speed and with substantial gas introduction so that it functions more as an aerator and less as a. pump to increase the flotation of the slimes without providing enough circulation and suspension to; cause any substantial scouring of the slimes by the coarse fraction.

This action is repeated through a sufficient number of cells to float ed a major portion of the valuable constitu-tent in the fine size range and without any substantial flotation of coarse sizes in conjunction therewith. The final pulp discharge from this first group of cells constitutes a feed to a second group of cells, and if additional reagent is required in order to eifect the necessary coarse flotation, an intermediate conditioning stage may be provided if desired. In the second group of cells, the discharge passages 13 are of relatively small diameter to accommodate the discharge of only that portion of the pulp which cannot be made to pass over the weir, and preferably thewein'will belowenedand the capacityof the cell substantially increased to permit a much longer flotation time.- If desired,- the impellenmay: be operated at substantially higher speed: to effectively suspendthe .coarse sizes, and the size or numbenof the recirculation openings 33 and 38 may be increased to. satisfy the pumping-re? quirements ofthe impellerat suchspeed. control will result in asubstantial. flotationof the valuableconstituent vin the coarse size. range with. the. resultthat by the. time the succession of treatments. is completed, a major portion. of. .the coarse fraction. willlbe. concentrated. v.If desired, rougher cleaner operations may beemployed with the. concentrate of the first series.v ofcellsl fed, to a separatecleaner stagev for such series; and the concentrate of the. second group of cells fed to a-separatecleaner stage for that group of cells. -In thepracticeof. this process I'do not wish to be limited to the: structural features hereinbefore disclosed as suitedfor performingthe process. It'will beapparent in any arrangement permitting a fast circulation of. the coarse fraction through .the firstzgroup with a controlled circulation ofthe slime sizes willsatisfy the objects oflthis process... Following. said first separation any: suitable control tocffect the flotation of the: major part of thecoarse; fraction. willjsatisfythe requirements. While I do. not wishto be limited to. acriti-r cal size range, an ore pulp having mixed sizesinthe '-8, range may be considered asa typical coarse fraction, while the 100 sizes including a substantialportion off-250- meshwill be considered atypical slim'es fraction.v The middlings. recirculationthrough the openings 38 may be assisted by mounting-:ahood 'or cover on the column 25 in overhanging relation to thesopenings. to avoid any vortex formationand prevent entrainment of mineral-carrying froth which has risen to. thesurfiaceoThe middlings so entering.thecolumnwill entrain substantial quantities of air-and produce a. splash mixing ef,- fect .on meeting. the entering feed streams and the recirculating pulp. admitted through the openings. 33. As a consequence, the pulp streams passing onto the impeller are pre-aera'ted and. receive the final aeration, and dis.- persion effect within the impeller enclosure-.y

I claim? i 1 In aeration apparatus of. the type, having a. rotary shaft carrying an impeller adjacent its lower end, a hollow column extendingupwardlyfrom a plane in proximity to the upper surface of said impeller and spaced from said shaft in enclosing relation. thereto for delivering an aerated pulp. ontothe impeller, the improvementwhich -comprises an upright tubular member carried by and rotatablewith said sh ft in spacedv relation to. the. impeller, said member being disposed between saidshaft and said column and. defining therewith. a: plurality of; passages for dividing a descending pulp flow onto said. impeller in separate. streams, there being a restriction in each passage for accelerating pulp flow as it approaches thaimneller, and: means in eachpassage mounted for rotation with said shaft for inducing an accelerated flow .throughjthe. pas;- sage. and. past said restriction. I y

2 ..'In aeration apparatus of the ty pe having a rotary shaft carrying an impeller low column extending upwardly from a plane in proximity to the upper surface of said empeller and spaced from said shaft in enclosing relation thereto for delivering an aerated pulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pulp flow onto said impeller in separate streams, there being a restriction in each passage for accelerating pulp flow as it approaches the impeller, and means in the innermost pas sage mounted for rotation with said shaft for inducing adjacent .itslower end, .a holan accelerated flow through said passage and past the restriction.

3. In aeration apparatus of the type having a rotary shaft carrying an impeller adjacent its lower end, a hollow column extending upwardly from a plane in proximity to the upper surface of said impeller and spaced from said shaft in enclosing relation thereto for delivering an aerated pulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pulp flow onto said impeller in separate streams, there being a restriction in each passage for accelerating pulp flow as it approaches the impeller, and-a plurality of pumping vanes supported from and rotatable with said shaft in each said passage for inducing an accelerated flow through said passage and past the restriction.

4. In aeration apparatus of the type having a rotary shaft carrying an impeller adjacent its lower end, a hollow column extending upwardly from a plane in proximity to the upper surface of said impeller and spaced from said shaft in enclosing relation thereto for delivering an aeratedpulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pulp flow onto said impeller in separate streams, there being a restriction in each passage for accelerating pulp flow as it approaches the impeller, and a plurality of radial pumping vanes supported from and rotatable with said shaft in each said passage for inducing an accelerated flow through said passage and past the restriction.

5. In aeration apparatus of the type having a rotary shaft carrying an impeller adjacent its lower end, a hollow column extending upwardly from a plane in proximity to the upper surface of said impeller and spaced from said shaft in enclosing relation thereto for delivering an aerated pulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pul'p flow onto said impeller in separate streams, there being a restriction in each passage for accelerating pulp flow as it approaches the impeller, and a plurality of pumping vanes interconnecting said shaft and the upper end of said tubular member whereby said tubular member rotates with said shaft and said vanes induce an accelerated flow through the passage between said tubular member and said shaft.

6. In aeration apparatus of the type having a rotary shaft carrying an 'inpeller adjacent its lower end, .a 1101- low column extending upwardly from a plane in proximity to the supper surface of said impeller and spaced from said shaft in enclosing relation thereto for delivering an aerated pulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pulp flow onto said impeller in separate streams, there being a restriction in each passage for accelerating pulp flow as it approaches the impeller, and a plurality of pumping vanes interconnecting said shaft and said tubular member intermediate the ends of said tubular member, a plurality of pumping vanes supported on said tubular member and extending into the passage on the exterior of said tubular member whereby said tubular member rotates with said shaft and said vanes induce an accelerated flow through said passage and past said restriction.

7. In aeration apparatus according to claim 6 in which the pumping vanes on the exterior of said tubular member are substantially larger than the pumping vanes on the interior of said tubular member.

'8. In aeration apparatus of the type having a rotary shaft carrying an impeller adjacent its lower end, a hollow column extending upwardly from a plane in proximity to the upper surface of said impeller and spaced from said shaft in enclosing relation thereto for delivering an aerated pulp onto the impeller, the improvement which comprises an upright tubular member carried by and rotatable with said shaft in spaced relation to the impeller, said member being disposed between said shaft and said column and defining therewith a plurality of passages for dividing a descending pulp flow onto said impeller in separate streams, means including a restriction in each passage for accelerating pulp flow as it approaches the impeller, a plurality of pumping vanes supported from and rotatable with said shaft extending into each said passage for inducing an accelerated flow through said passage and past said restriction, and an outwardly directed, annular flange disposed at the lower end of said tubular member for directing said accelerated flow substantially parallel to the top surface of the impeller, there being a plurality of openings in said impeller underneath said flange for directing a portion of said accelerated flow underneath the impeller.

References Cited in the file of this patent UNITED STATES PATENTS Serial No. 419,507, Sborlino (A.P.C.), published May 25, 1943.

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