US2337806A - Flotation machine - Google Patents

Description

Dec. 28, 1943. A,Iw FAHRENWALD 2,337,806

FLOTATION MACHINE Filed Oct. 21, 1941 2 Sheets-Sheet 2 ATTORN EY on in a continuous manner Patented Dec. 28, 1943 UNITED STTES PATENT` OFFICE FLorA'rroN MACHINE Arthur W. Fahrenwald, Moscow, Idaho Application october ai, 1941, serial No. 415,893

` s claims. (ci. 20a-169) VThis invention relates to a flotation machine which, among other uses, is particularly useful in ore dressing methods or processes in which it is desirable to agitate, circulate, and aerate mineral bearing liquids.

In the conventional practice relating to the flotation of Amineral particles to eflect separation from the conveyant liquid, it is the usual prac,- tice to employ a cell or a series of cells into which a stream of mineral bearing liquid is introduced, treated to aerate the material and then conveyed away for disposal. Such cells are usually provided with an impeller, either of the rotary or oscillatory type, and, when material to be treated is introduced to the cell, these impellers circulate it, agitata it, and aerate it to produce a froth which rises to the surfa of the contained liquid and carries with it 4minute mineral particles. Often the frothing action is enhanced by the employment of frothing agents, such, for example, as improve the production of the froth and increase the atfnty of mineral particles being separated and the bubbles ofthe froth. The froth rises to the surface of the cell and forms a blanket which' may be skimmed or otherwise drawn off.` The operation of such notation cells is usually carried and, as material is fed to the cells to be treated, other material is drawn off the cell for subsequent treating stages or otherwise to be disposed of according to the dictates of the process. The froth that is skimmed from the cell is'conveyed away for further treatment and such treatment may include settling, concentrating in lters or other dehydraters, or drying by exposure to air.

Among important objects of my invetnion, one object is to improve pulp agitation in the flotation machine.

Another relates to improving the pulp handling in a cell in the manner in which it is collected and discharged from the cell after being subjectedto the action thereof.

A further object is to simplify the pulp aeration, agitation and circulation means and consequently to improve the operation of the unit.

Another object of my invention is the provision of an improved primary pulp feed for a flotation cell so arranged that the fed material is delivered to the impeller adjacent its upper face to insure the pulp being acted upon by the impeller as soon as introduced to the cell.

pine oil and other suitable chemicals which A further object of the invention relates to the provision of means whereby internal pulp recirculllation may be effected within an ce Still another object of the invention is to provide auxiliary pulpfeed means that may operate simultaneously to the primary pulp feed for effective retreatment of certain materials,

A still further and important object of the invention has been the provision of novel pulp outlet means including a pulp launder located centrally of a cell to raise the efficiency of such operation and to eliminate lcross-currents in-the pulp flow and its detrimental 'effect upon the froth produced.' And in this connection, an associated object has been the provision of novel means'forv controlling the pulp level and for permitting the outgoing flow of pulpv from a. zone below its surface. y

. Still other and further objects of invention are to provide novel inter-cell conduit means for handling the iiowV of pulp and air and also to provide anti-swirl means adjacent the impeller for deflecting and directing agitated and aerated pulp to enhance the formation of the froth.

Another object of the invention has been to lncorporate all the foregoing-objects in a single unitary mechanism that is simple to construct, that will operate continuously with low maintenance and operation cost. and that will produce results highly improved over conventional practices.

Other objects and advantages of the invention will be more apparent during the course of the following description, wherein I have set forth 'and described a preferred lembodiment of my invention. This description, taken in view of the accompanying drawings, constitutes a full disclosure of the invention and serves as a basis for the subjoined claims.

Throughout the various views of the drawings, like reference numerals refer to like parts and in individual v the drawings, Y

Figure 1 is a vertical, longitudinal sectional view through a pair of cells on the axis of the impeller,

Figure 2 is a fragmentary, sectional view similar to Figure l, but showing certain parts of the flotation cell of my invention in elevation, Y

Figure 3 is a lateral section of a single cell as though taken at right angles tothe showing oi Figure l along the impeller axis,

Figure 4 is a vertical, sectional viewof my launder showing the outlet conduit associated therewith for the handling of pulp and air to an adjacent cell or to other disposal means,

Figure 5 is a cross-section taken 0n lines 6-5 associated therewith.

of Figure 3 showing the details of an impeller and an associated anti-swirl-gauge, and

Figure 6 is a horizontal sectional view of a pulp inlet chamber and illustrating conduit means `I employ a cell for myr flotation machine which comprisesa bottom I having a back wall I2,

a front wall I4, that may be directed outwardly, as at I5, and which terminate in an upper overiiow lip I6. Theside walls I8, I8 ,andv 20 join with the front and backrwall according to.- the showing of Figure 1 to provide a pair of adjacent cells'that are shown as rectangular in shape but which may be 'formed in any suitable shape laccording to the requirements of space and the manufacturing processes, For the passage of Ypulp through the cells, the walls I8, I8and 2|!V may be ported at 2|, 22 and 28 respectively as desired.

The operating mechanism of the particular flotation cells shown herein, is mounted on asuperstructure comprising end plates 24 and V28 supported upon suitable structural members 28 in the cell and in turn. supporting'anoverhead .crossmember VSII shown to be tubular. 1 Upon the cross memberi30, and by'means oiv brackets ,8i and 3 2, a mounting plate 33'1or the motorn3 4 is provided. As, shown in Figurer 3 the motorl has a pair of sheavesj.v and. adapted to re-;

belt for-purpose'slater to be deceive a `drive scribed. A g lA bearing base plate, 38:,is attached to .the

vmember and, Vupon this plate l Amount the spindle bearing 40 adaptedl to receive andijournal the impeller spindle shaft 42, '42.'

The shaft `42vpasses through the bearing 40 and on its upper end is provided a sheave A43 or vUI. yThe belts 45 and 46 pass around the driverl sheaves 44,44`and aroundthe drive sheaves 38 and 35, respectively, so that when theV motor is actuated inthe customaryA manner, and its above, and approximately centrally located with respect to the axis of rotation of the impeller. The housings each have-lower discharge openings 58 and upper openings V59 which, in the case of theoverhead drive illustrated herein, accommodates the impeller shaft. A lid or cover plate closes each of the openings 59 and encircles the shaft 42 to reduce unrestricted recirculation of the pulp in the cell through the opening 58.

In' certain cases, the opening in the lid 60 may however be looseenough in its ilt around the shaft to permit limited recirculation of pulp.

Communicating with the chamber 51 and extending Voutwardly at one side of the housing,

isthe' primary feed inlet 62 whichin the instant .v case, is directed downwardly to the housing from 'an upper elevation.

sheaves caused to rotate, rotary motion is transmitted'to the shafts 42. Y Y

At its lower end shaft' 42 is coupled to the base plate 48 ofthe impeller. Upon the base plate and arranged in any su'table manner such, for example, as the radial showing of Figure 5, are a plurality Vof impeller blades '50;v Upon theirfupper surfaces the blades arejoined'to'the cover-plate 5I that has 'ar central port-52;v The impeller thus described is what is know'nas ."closed type of impeller butit is pointed out that other types may be used without departing from the principles of my invention so long as it is adapted to introducevfed pulp at or adjacent the center of the impeller. YIncertain instances such impellers mayk be driven from below and l do not wish to be limited, therefore, to the overheadl drive herein shown and described'as it merely exemplifies my I eliminate vortical swirling of the material loeing discharged from the impeller byemploying a pluralityy of deilector blades 54 arranged around the impeller in the mannerlof a cage. rlis shown' in Figure 5.the, plane of the deiiector blade is disposed'away from the plane of the radial blades ofthe impeller so that material leaving the irnpeller may strilzeY against its'face and be brought` to rest Ymomentarily in "order'f that air bubbles, and froth that isfoarning in the mass, can be given an opportunityto start ascending through the pulp to theupper surface. v

For the'pu'rpos'es 'of feeding pulp through the impeller, Iemploy yhollow cylindrical yhousings 55 which form the feed chamber 5l in eachfcell v shown in the drawings.

` In the case of a multi-cell structure as vshown in Figure 1 it is customary to employ a primary feed conduit 64, associated with wall opening 23, and alsecondary feed conduit 66 communicating between the cells through the opening 22, both vof which are adapted to receive an auxiliary vent tube 68 orbe closed by a plug 69 according to the, n

dictates of operation of the flotation machine. Pulp is fed through the primary inlet conduit 8,4 and flows down the inner inclined tube into the housing, out through the opening 58 to thel impeller, and thenV isv aerated and circulated in the usual manner.A Y Y .Disposed centrally of the cell and surrounding the' vertical impeller shaft, in the case of the overhead driven impeller, is my pulp launder` the cell by means ofthe launder may beexposed to free air.` Y l Under certain circumstances it is desirable to vary the, pulp level within lthe cell. This is accomplished by providing the tubular hollowcylindrical gate 'I8 positioned in the riser I4 so that the outgoing pulp must rise to its upper terminal before'V leaving the cell. In this way the pulp level is denedfin the cell. i

Thegate 'I6 has a draw bar 'I8 attached to It and rises therefrom passing through the bracket I8 on thersuperstru'cture, here shown attached to the kbearing member 40. Threads at on theA draw bar are for the reception of a hand wheel 8 I. By turning the hand wheel in one direction or the otherthe draw bar and gate are raised or lowered as desired.` v

As pulp iiows `outwardly from' the launder through the outlet 12,it may leave the cells' through an intermediate lconduit member 84 or through arterminal conduit 85 associated with opening 2|. I prefer that gravity be employed toenhance the flow of the outgoing pulpand for thatreason have disposed my conduit system'at anangleto the horizontal positionfdependlng from the cell-Which is discharging pulp into the cell which receives the discharged pulp or downwardlyV into suitable pulp disposal means `not Under certain conditions it is necessary to eliminate heavy sand in the conduit thatis present in the pulp. Suitable outlets as 86 are provided. In the showing ofthe drawings these outlets are closed by plugs 8l but it should be apparent that such material may be piped away from this point by any conventional means.

As the bubbles formed in the'pulp rise to the upper surface and Joint the froth blanket thereabove, between the levels A and B, it is caused to pass out of the celloverthe overflow lip I6 into the froth launder 90. A paddle wheel comprising the shaft 92, arm 93, and blades 94, Journaled in suitable bearings 95 0n the frame of the iiotation cell, is rotated through -power applied to the sheave 96 by the belt 91that is in turn driven by vsheave 98 on a shaft 99. A reducer element for the shaft 99 is indicated at |00 and a motor lili rotates the elements of the speed reducer so that a relatively slow rotation is eifected in the paddle wheel arrangement. Asthe blades 94 sweep in their respective arcs they engage and urge a portion of the froth blanket over the lip I6 for disposal in the launder 90.

In operation pulp enters the cell from the side and is conducted to the approximate axis of the impeller .and discharged thereto. Through the rotation of the impeller it is circulated and ejected outwardly into the cell and against the blades of the deflector blades where bubbles formed therein begin their ascent through the pulp.

The entire tank, comprising an individual cell, is filled with pulp to a level defined by the gate 16, and, by my means, I have found that it is possible to obtain great and concentrated agitation in the neighborhood of the impeller and a relatively quiescent condition in the upper zone of the cell so as not to impede or restrict the movement of the rising froth.

The outgoing now of pulp rises under the lower lip of the riser 14 and passes therethrough and also through the gate 'i6 where it overflows around the upper periphery of the gate into the launder basin 10. It is preferable that this outgoing ilow be sufficient to fill the conduit approximately one-half full so that air may be drawn into the pulp by reason of the suction created in the lower ends of the conduit and-adjacent the impeller..

In the case of the right cell in the showing of Figure l, if it is desired to introduce auxiliary air the plug 69 is removed and the conduit or vent tube 68 is inserted in its place rising above the pulp and froth levels so that air may enter under the urgence of the suction at the impeller.

Internal pulp recirculation inV a cell may be obtained by eliminating the plug 69 from the conduit and permitting pulp to flow through this opening-or recirculation may be obtained by varying the size of the opening in the lid 69 so that pulp may flow downwardly into the housing 56 and closing the chamber. Auxiliary pulp from other than the primary source, may be introduced to the feed housing 5B through an auxiliary pulp conduit lill shown in Figure 3. When not used the boss Ill, in the housing. is usually closed by aplug H2. (See Figure 2.)

In the operation of the cell, pulp is caused to travel outwardly from the impeller in the wellknown manner of the operation of such a device. Upon striking the deflector blades 54 the swirling motion is arrested and the pulp rises in the tank during which period the propagation of air bubbles occurs. The bubbles, having an afiinity for metallic particles, rise from the pulp and form the surface froth. Excess pulp is withdrawn from the cell in the middling zone by means of the launder which gathers the outgoing material. Since the opening from the cell to the launder is axial thereof above the impeller and belowl the surface of the pulp, the path of travel of the pulp current is downward from where the aerated pulp leaves the mass at the surface. It

can be seen that the path of travel of the pulp 4 just prior to where the pulp enters the launder. 'The phrase "just prior to is used with the thought that where objects are travelling in a path, a station in that path is just prior to another station whenin the sequence of Vtravel one precedes the other counter to the direction of travel. Thus it will appear that the pulp is induced to travel in aseries of inverted curved paths symmetrical of the cell and in these paths the pulp has the froth removed just prior to its leaving the cell through the launder.

In those cases where the pulp is permitted to recirculate into and out of the impeller, the Path becomes ring-like rather than merely curved since there is then a partially closed circuit. In such a closed path the principal-stations are those where force is applied by the impel1er.where aerated pulp is removed, where the excess pulp is removed andI finally where the pulp being recirculated is returned to the impeller.

Having thus described my invention, I claim:

1. 'I'he process oi.' otation of ore bearing pulp contained in' an open Icell, which process comprises: aerating and moving the pulp in a plurality of closed curved paths the axes of which .lie 'in a closed curve within said cell, removing aerated pulp at a similar station in each of said paths, and gathering an increment of the pulp from each said paths at another station thereof similar throughout the series, said removal statiohs being situated in said paths just prior to and outward of said gathering stations of the paths with respect to the axis of the cell. said gathering stations being below the pulp level of the cell.

2. The process of flotation of ore bearing pulp contained in an open cell, which process comprises: aeratlng and moving the pulp in a plurality of ring paths whose axes lie in a closed curve within said cell, removing aerated pulp at a similar station in each of each said paths, and gathering an increment of the pulp from each said paths at another station thereof similar throughout the series, said removal stations being situated in said paths `iust prior to and outward of said gathering stations of the paths with respect to the axis of the cell, said gathering stations being below the pulp level of the cell.

3. The process of flotation of ore bearing minerals contained in an open cell, which process comprises: aerating and moving the pulp in a plurality of curved paths whose axes 11e in a closed curve within said cell, removing aerated pulp from each said paths at similar stations thereof, gathering an increment of the pulp in each said paths at other similar stations of each similar throughout the series, said removal stations being situated in said paths with respect to the axis of the cell just prior to said gathering stations and below the pulp level within the cell,

portion of the pulp for recirdrawing at least a portion of the pulp from its f path in the cell, said pulp removal station ln said path being outwardly located in said cell with respect to the pulp withdrawal station in the same path whereby the withdrawal from the cell is of pulp from which the froth portion has largely departed.

5. Flotation mechanism comprising: an impeller for aerating and circulating pulp` in a cell so that the pulp travels in an outwardly ascending curved path, means for removing a froth portion of the pulp at the pulp level from the cell, and means for withdrawing at least a portion of said pulp from its path in the cell at a station below the pulp level of the cell, said withdrawal means comprising a cylindrical launder in said cell rising above the froth and having a lower inlet opening centrally located in the cell to draw material symmetrically from said cell below its Y pulp level, whereby the froth portion is removed at a station Just prior to and above the pulp ywithdrawal station in said path, and means in said "launder above said inlet for determining the pulp level of the cell.

6. Flotation` mechanism comprising: an impeller for aerating and circulating pulp in a cell so'that thepulp-travels in an outwardly ascendying curved path, means for removing a froth portion of the pulp at the pulp level from the cell, and means for withdrawing at least a portion of said pulp from its path in the cell at a station below the pulp level of the cell, said withdrawal means comprising a hollow cylindrical launder having an upper opening rising above the froth level of the cell, said launder having a lower inlet opening axial of the cell to draw material symmetrically therefrom below the pulp level,

whereby in said path the aerated portion is removed at a station just prior to and above the pulp withdrawal station, and means in said launder above said inlet for determining the pulp level of the cell. l

- i ARTHUR W. FAHRENWAID.

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