US2502497A - Froth flotation apparatus - Google Patents

Description

April 4, 1950 P. WIGTON mom FLOTATION APPARATUS s Shets-Sheet 1 Filed Oct. 10, 1944 PAUZ L. Wmraxv IN VEN TOR.

ATTORIVEY April 4, 1950 P. L. WIGTON 2,502,497

F'ROTH FLOTATION APPARA'IUS Filed Oct. 10, 1944 3 Sheets-Sheet 2 PAUL. L. WIGTON v INVENTOR.

ATTORNEY April 4, 1950 P WIGTQN} 2,502,497

mom FLoTA'rIoN APPARATUS Filed Oct. 10, 1944 3 Sheets-Sheet 5 I l 67 I6 "i 8 66 67 8 26 6a m x R 4 I 65 "C El F WI PAUL L. WWGTON INVEN TOR.

AT TORNEY Patented Apr. 4, 1950 UNITED STATES PATENT OFFICE FROTH FLOTATION APPARATUS Paul L. Wigton, Denver, Colo.

Application October 10, 1944, Serial No. 557,968

12 Claim.

This invention relates to froth flotation apparatus and treatments and more particularly relates to improvements in the mixing and aerating action of flotation apparatus of the mechanical agitation type.

In the usual mechanical type flotation machine an ore pulp is fed into a flotation cell substantially filled with pulp and is mixed with air or other gas, and in some instances reagent, by the action of an impeller rotating in the pulp body. Aerated pulp.on being discharged from the zone of influence of the impeller circulates through the cell with mineral particles coated by the reagent rising to the surface and collecting in a froth under the elevating influence of the aeration.

The present tendency in all ore milling operations and particularly with flotation equipment is to use larger size machines. This in turn requires larger impellers, and in some instances at least, more high speed rotation of the impeller, all of which conditions tend to cause an undue turbulence in the cell and excessive wear on exposed parts. It is an object of the present invention to provide froth flotation apparatus which will provide a high degree of aeration and recirculation of pulp in each cell without causing undue agitation.

Another object of the invention is to provide an intense mixing of pulp, gas, and reagent within the impeller element of a mechanical type flotation cell.

A further object of the invention is to provide a novel type of circulatory action in a multicell flotation machine.

Other objects reside in novel combinations and -arrangements of parts all of which will be described in the course of the following description.

Briefly stated, the present invention comprises a series or sequence of mixing actions within the confines of a rotary impeller to mix incoming pulp, recirculating pulp, gas, and reagent and distribute the intermixture throughout a flotation cell. Certain features of the impeller structure per se, not claimed herein have been claimed in my copending application, Serial No. 95,095, filed May 24, 1949. The apparatus of the invention will be best understood by referencev to the accompanying drawings illustrating typical embodiments of the invention.

In the drawings, in the several views of which like partshave been designated similarly,

Fig. l is a front elevation, partially broken to show interior parts in section, of a multi-cell flotation machine of the mechanical agitation type embodying features of the present invention;

Fig. 2 is an end elevation of the feed or inlet end of the machine shown in Fig. l;

' Fig. 3 is a section taken along the line 3-3, Fig. 2;

Fig. 4 is a top plan view, partially broken, of an impeller assembly of the type shown in Fig. 1; 5 is a section taken along the line 5-5,

F Fig. 5a is a section taken along the line 5a5a,

Fig. 6 is a top plan view of a feed distributor Ia. sse1;ibly of the type used in the machine of Fig. 7 is a vertical central section through a cell of a modified type of flotation machine embodying features of the present invention; and

Fig. 8 is a section taken along the line 8-8, Fig. 7.

' Referring first to the form of the invention shown in Figs. 1, 2, and 3, a multi-cell flotation machine has been shown, comprising a tank T comprising end walls I2 and I2 a front wall l3, a rear wall It, and a bottom 15. The interiorof the tank is divided by a series of partition members It and "l into a series of cells C C and C here shown as three in number, but which may be any number, and the tank has a feed inlet l1 into cell C and a discharge outlet i8 from cell C The top of wall l3 terminates in a froth overflow lip l9 above which a rotary skimmer 20 is mounted to assist in the overflow of froth from each side cell. A hollow rotary shaft 2| is journalled in a bearing unit 22 supported on superstructure S mounted above tank T, and this shaft is driven by a motor M through the intermediary of sheaves 23 and 24 and transmission belting 25.

The features thus far described are more or less conventional in flotation machines of the mechanical agitation type and, per se, form no part of the present invention. An impeller assembly I, the details of which will be described subsequently, is mounted at the lower end of shaft 2|, and a feed distributor assembly F extends from a wall of the cell to terminate in overhanging relation to impeller I.

The assembly F is attached to the cell wall, as for example wall I 6, as by bolting and is held at its suspended end by a rod 26 supported from superstructure S and having a threaded connection with the distributor assembly. A-reagent conduit comprising a funnel member 21 and a conduit member 28 is supported from assembly F in communicating relation to its hollow interior.

The impeller assembly I comprises a. lower disc or plate member 30 and an upper disc or plate member 3|, both of which are keyed on the shaft for conjoint rotation in spaced but proximate relation. A series of slicing vanes 3|! positioned at intervals about the periphery of disc incline slightly to the periphery and a second set of pumping vanes 3|) are arranged substantially radially at intervals about a central hub portion 30 The upper or feed disc member 3| comprises an outer annular portion 3 I, an inner spider portioncomprising a plurality of spaced spider arms 3| and a central hub 3|.

Feed to the machine enters through inlet I! to enter distributor F from which it descends through the openings in the spider portion and is sliced or cut by the rotating spider arms 3| of disc 3|, before passing onto the surface of lower disc member 30 where it is ejected by the centrifugal action across the periphery of said disc. At the same time blades 3|) slice into the pulp at the periphery of disc 30 and draw same interiorly of the disc until it meets the outwardly traveling stream and is diverted thereby to travel back across the periphery at the end of the vane 30*.

Gas under pressure is fed down through shaft 2| and passes out through a series of radial ports 33 into the enclosure formed by the discs 30 and 3| to mix with and aerate the incoming pulp streams. As will be best understood by reference to Fig. 6, feed distributor assembly F preferably comprises a conduit section 34 and two nozzle sections 35 and 35 preferably joined as by bolts 36 to provide a bifurcated outlet portion.

The bifurcated portions 35 and 35 extend around shaft 2| in closely spaced relation thereto, and provide a channel adjacent their ends through which recirculating pulp may descend onto the impeller. In addition, the lower edges of said portions are substantially spaced from the top of disc 3| as clearly shown in Figs. 1 and 3, thereby permitting pulp to flow into said space under the pumping action of the impeller and thus provide additional recirculation.

The impeller I, although formed of separated top and bottom members, is, in effect, a closed type impeller. The pulp descending through the channel in distributor F and entering the impeller through the space between the distributor and the impeller descends into thespaces between the spider arms 3| and is broken up by said members, which are of rhomboid section as shown in Fig. a to provide a cutting edge at the forward angle of such section.

After being so acted on, the incoming feed anr' recirculating pulp fall within the impeller en closure and there mix with other pulp and the gas within said enclosure, as well as reagent if introduced through conduit 28, and finally discharge from the enclosure under the centrifugal influence, So much of the aerated pulp as passes well beyond the periphery of the impeller assumes a circulatory course through the machine, while other portions of aerated pulpadjacent the periphery are drawn back into the enclosure by the vanes 3|) and are subjected to further mixing within the impeller.

As a result of this sequence or series of mixing actions the gas is thorough diffused and large bubble formation is prevented, and surface contact between individual particles of the pulp and the reagent and between said particles and the 4 I the purpose of the aeration. Due to the high degree of mixing within the impeller it is not necessary to run the impeller at high speeds, and by using gas under pressure introduced through the hollow shaft, any amount of gas, within limits, may be introduced into the pulp.

Consequently, the speed of the impeller is gcv erned primarily by the pulp-circulating requirements of the machine rather than from the standpoint of its gas-drawing capacity and may be run at a speed which will not produce undue turbulence and excessive eddy currents as might otherwise occur. At all such speeds the centrifugal movement of material within the impeller is more than adequate to provide all of the mixing steps of the type hereinbefore described.

Any suitable arrangement for the gas introduction may be provided, but I have found that highly satisfactory results are attained by using the arrangement shown in Figs. 1, 2, and 3. This constnuction is shown and claimed in Weining Patent No. 2,198,143, owned by the assignee of record, and per se forms no part of the present invention.

As shown, the gas introducing system comprises a header 40 supported from superstructure S and extending lengthwise of the tank with branch, valve-controlled conduits 4| connecting the header with a hollow, air-sealed chamber 42 within bearing unit 22. One or more, preferably two, openings 43 are provided in the portion of hollow shaft 2| within the enclosure of chamber 42 to admit gas under pressure from said chamber into the interior of the shaft, from which it discharges at the ports 33.

Through this arrangement selective aeration of each cell can be effected and by maintaining a maximum pressure in the header, in excess of normal requirements, any required gas pressure can be delivered to a given cell. The valves controlling the flow through branch conduits 4| provide a simple and easy control for the operators convenience.

Circulation of pulp from cell to cell throughout the machine is controlled by a series of gatetype overflow weirs 45 movable along a partition member 46 to change its effective elevation. The weir setting is controlled by screw mechanism 41 actuated by a hand wheel 48. These weirs 45 are located in an overflow compartment 49 formed by the spacing of partition H5 of a preceding cell and partition l6 of a succeeding cell.

An opening 50 in each partition member l6 permits a pulp discharge from its associated cell into the adjoining compartment 49, and an opening 5| in each wall I6 conducts pulp into the associated distributor member F. Pulp flowing out of the last cell C of a given series enters a discharge compartment 49 formed by partition ll; and end wall l2 and thence passes through outlet conduit I8 into a tailings discharge box 52, having a nipple 53 for connection with any suitable conduit member.

Through these provisions for circulation control it will be apparent that individual weir settings may be made to control the level in each cell selectively. Pulp passing from one cell overflows the weir 45 and descends into and through the next feed distributor conduit F by gravity to the impeller I of the succeeding cell. The action as previously described is repeated in each impeller with aerated mineral rising to the surface and collecting in a froth which discharges across overflow lip l9.

Some of the non-floated mineral is recirculated through the impeller as previously described while other ortions pass through opening and overflow the weir to pass into the next cell. This action is repeated through the series of cells with the. final tailings discharge passing from this treatment through compartment 49" and discharge box 52.

It will be apparent that for some purposes it will be desirable to vary the amount of pulp recirculation in a given cell. This can be accomplished by adjusting the spacing between distributor F and impeller I. The adjustment is conveniently provided by elevating or dropping the end of rod 26 through the screw adjustment provided at its top.

I prefer to make distributor F in sections as illustrated for a two-fold purpose. In the first place the sections 35 and 35 can be made interchangeable with similarly shaped, conduit carrying sections, adapted to connect with the return nipples or 56 (Fig. 2) when the machine is to be adapted for rougher-cleaner operations. The openings 55 and 56 are normally closed by a screw plug (not shown) which is removed when a return conduit is connected to any said nipple.

A second benefit of the sectional construction is that in event of excessive wear on the portions overhanging the impeller, such portions may be removed without disturbing the shaft setting, and suitable replacement can be made in the same manner.

6 By having the intake of the recirculating system adjustable, it is possible to vary the elevation at which such product is removed. Also, by locating' feed intakes in the corners of the cell, the withdrawal of the high density material is effected without material impediment to the normal flotation action as the rising mineral has substantially the entire area of the cell to move through in passing into the froth.

It will be apparent from the foregoing description that the machine just described is capable of attaining all the aforementioned objects of the invention and is simple and durable in construction, as well as being economical in operation.

Certain of the features hereinbefore described are intended to be utilized in conventional type The bifurcated shape of the distributor F, permits a simple impeller removal action when required. The bolts holding the bearing unit 22 on superstructure S are loosened to permit the shaft and impeller to swing out beyond the end of distributor F to a position in which it can be elevated without contacting the distributor.

In order to confine the agitation within the lower portion of the pulp body, I provide a series of 'baflies 60 of a well known type to overhang the impeller and associated parts. This structure also may be used to support a recirculation unit of the type shown in Figs. 7 and 8. The cell 0* shown in Figs. 7 and 8 is identical with cell C except for the addition of the recirculation unit and accordingly the corresponding parts have been given the same reference numerals.

The recirculation unit R. as shown in Figs. '7

and 8 comprises an open ended housing adapted to fit into the channel in distributor F and having in its top a series of branch conduits 66 referably arranged in the form of a lower radial portion and an upper upright portion. Each of the branches has a cage member 61 at its upper end, adapted to receive and hold a series of ring members 68 for varying the effective elevation of the upper end of each said branch.

In many flotation operations, there is a tendency for a high-density zone to form in the upper Fig. 8, it is possible to remove a substantial por- I tion of the solids of such a high density zone for retreatment at the impeller, particularly to coat the particles so they will float more readily.

mechanical flotation machines. For example, it will be apparent that the impeller and feed distributor assembly may be utilized in various well known machines, or the impeller unit alone may be used for operation in various machines adapted for the use of closed-type impellers. In this connection it is noted that while the introduction of gas under pressure through the hollow shaft represents a preferred embodiment of the invention, the impeller runit discussed herein will function efficiently with gas introduced underneath the impeller or adjacent the periphery of its lower disc member. This is true because the slicing vanes at the periphery of the impeller are capable of drawing in considerable quantities of gas and aerated pulp to mix with the incoming pulp within the confines of the impeller.

Other structural changes are within the contemplation of the present invention. For example, I have shown a convenient arrangement for reagent feeding, but in the use of certain types of reagent it may be preferable to feed the reagent into the feed compartments 49 and thence to the impeller through the feed distributor F in order to provide a longer reaction interval and conditioning time. Similarly the location of the branch conduits 66 may be changed to different points within the cell, and these conduits may be a flexible composition such as rubber in order to facilitate location at any desired position within the cell.

As shown in Fig. 4, the preferred arrangement for introducing gas from the hollow shaft into the impeller enclosure is through the series of radial ports 33, the outlets of which are positioned at a distance from the vanes 30 against which the discharged gas is directed. Under some circumstances it may be desirable to provide a longer travel for the discharged stream of gas before it begins mixing with the pulp and a convenient arrangement for such an action is to locate the ports 33-so that the direction of discharge is substantially parallel to the adjoining vane 30 and immediately at the side of same.

To further facilitate the passage of gas toward the periphery the vane 30 may be grooved lengthwise at the approximate level of the gas stream to provide a path along which the gas moves before brought into mixing contact with the pulp. In this way, most of the pulp-gas intermixing will occur underneath the annular portion 3P of member 3| in the region of contact of the co untercurrent streams previously described.

A further advantage of the impeller designs hereinbefore described is that the arrangement of the feed distributor F and double disc impeller assembly I prevents sanding up during shutdowns and the like, which otherwise would interfere with the starting of the impellers when the machine operation is resumed. The channel in the distributor member F permits some sands to settle into the impeller when the machine is stopped, but the amount of such sands that enters therethrough is substantially less than the amount the impeller can accommodate in the starting action. Due to the close spacing of the distributor from the impeller, light, if any, sands will enter the space between these members and the top plate of the impeller shields the enclosed portions so that little, if any, sand settles onto the impeller from a point below distributor F. Consequently, even after a protracted shutdown, it is safe to start the machine in the usual way without special handling of the settled solids.

Therefore the description and accompanying drawings are intended to illustrate a preferred embodiment of the invention but not to limit the same, the scope of the invention having been clearly set forth in the hereunto appended claims.

What I claim and desire to secure Patent is: e I

1. In froth flotation apparatus of the character described, a tank for pulp, a rotaryimpeller in the tank comprising two superposed discs, the

lower disc having a series of slicing vanes ar-.

ranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, and means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially leover said central opening and deliver pulp thereto.

2. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulpinto the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend radially through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, and means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto.

3. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tan: comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller. and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, and means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller thereto to substantially cover said central opening and deliver by Letters 8. pulp thereto, said conduit being spaced from the top surface of the impeller a suflicient distance to permit a recirculating flow into the central opening.

4. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, and means for feedingranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, and means for feeding pulp onto said impeller, including a conduit having bifurcated portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto.

6. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms of rhomboid section arranged to extend through said open portion and deflect pulp downwardly through the opening, and means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto.

7. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of aid disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller in spaced relation thereto to substantially cover said central opening and deliver pulp thereto, and means to vary the spacing between said impeller and said overhanging portions.

8. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a serie of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing'arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto, and means associated with said pulpfeeding mean for delivering reagent to the impeller.

9. In froth flotation apparatus of the character described, a tank for pu p, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vane arranged about its periphery to draw pulp into the impeller, and a second set of pumpin vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially cover said central openin and deliver pulp thereto, and means associated with said pulpfeeding means for returning pulp from a point in the tank remote from said impeller directly into the impeller.

10. In froth flotation apparatus of the char acter described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulpinto the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller acros the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a-conduit'having portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto, and adjustable means for returning pulp at different elevations in the tank directly into the impeller.

11. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across the periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a conduit having ortion overhanging said impeller to substantially cover said central opening and deliver pulp thereto, and means for delivering gas under pressure into said impeller.

12. In froth flotation apparatus of the character described, a tank for pulp, a rotary impeller in the tank comprising two superposed discs, the lower disc having a series of slicing vanes arranged about its periphery to draw pulp into the impeller, and a second set of pumping vanes arranged on the disc to discharge pulp within the impeller across th periphery of said disc, the upper disc having a central open portion and a series of slicing arms arranged to extend through said open portion and having a forward cutting surface arranged to deflect pulp downwardly through the opening, means for feeding pulp onto said impeller, including a conduit having portions overhanging said impeller to substantially cover said central opening and deliver pulp thereto, and valve-controlled means for delivering gas under variable pressure into the impeller.

PAUL L. WIGTON.

REFERENCES CITED The following references are of record in the l file of this patent:

UNITED STATES PATENTS

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