US1374499A - Flotation apparatus - Google Patents

Description

'w. E. GR EENAW ALT.

FLOTATION APPARATUS.

APPLICATION FILED DEC.27, 1915.

Patented Apr. 12, 1921.

2 SHEETSSHEET 1.

Min

WQ'E. GREENAWALT.

FLOTATION APPARATUS. I

APPLICATION FILED 0 50.27, 1915..

Patented A 31 12; 1921.

2 SHEETS-SHEET Z- I WILLIAM E. GREENAWALT, or DENVER, COLORADO.

FLOTATION APPARATUS.

Spceffication of. Letters Patent.

Patented Apr. 12, 1921.

Application filed Deceinber 27, 1915. Serial No. 68,718.

To all whom it may concern:

Be it known that I, WILLIAM E. GREENA- WALT, a citizenof the United States, residing in the city and county of Denver and State of Colorado, have invented certain new anduseful Improvements in Flotation Apparatus, of which the following is a specification.

My invention relates to apparatus for the separation of mineral values; from their gangue by flotation, and has for its object the cheap, effective, and economical recovery of the mineral values by flotation in an apparatus which is cheaply installed and which is simple in operation.

This application is a continuation in part' of my pending application. Serial No. 58,748, filed October 30, 1915, and also a continuation in part of my pending applications, Serial No. 812,951, filed January 19, 1914- and Serial No. 845,011, filed June 13, 1914. i

In the accompanying drawing Figure 1 is a vertical section through the apparatus; Fig.2, a detail'section showing the method of introducing the material tobe treated into the liquid in the tank; Fig. 3, an alternative method for introducing and distributing the material to be treated into the liquid in the tank; Fig. 4, a'horizontal section showing a perforated hood or surface, and Fig.

5, a horizontal section showing a porous hood.

Referring to the drawings, 1 is a tank adapted to contain a liquid and the material to be treated. 2 is a hood suspended within the tank and submerged in the liquid, and having perforations 3 (or porous material 3 see Fig. 5) through which gases pass from the inside of the hood to the liquid in the tank. 4 is a shaft, a portion of which. 4 is hollow, rotating in bearings 5, by means of which the hood 2 is suspended and rotated within the tank when driven by the pulley 6. 7 is a feed hopper by means of which the material to be treated is fed into the tank through the stationary tube 24 within the hollow shaft 4*, and passing through the holes 35, enters the liquid in the tank either through the distributing pipes 30 or over the distributing surface 31. See Figs. 4 and 5. If it is desired to feed the material close to the shaft 4*, it is preferably fed through the pipes 30, and if it is desired to spread it in a thin sheet over the top of the liquid, it is preferably spread over the rotating surface 31. 8 is a pipe, preferably stationary, through which air or other gas may be dellvered to the submerged hood, communicating with the source of gas supply through 60 the pipe 9, having a gas regulating valve 10. The pipe 8 enters the mouth of the hood, and preferably. delivers the gas above the llqllld in the hood, although if the liquid enters the pipe 8, as it frequently may, no particular harm will be done, as 1t would againbe e rpelled by the air or gas. 11 is an opening'in the bottom ofthe tank through which the gangue may be removed bypassingdt through the pipe 12 and the regulating valve 13. If desired, the material may be returned to the tank for re-treatment through the plpes 14: and 15, or passed on to another similar apparatus, in series with it, for further treatment through the pipe 16. Air or other gas is introduced into the pipe l4; through the pipe 17, thus making an air-lift of the pipe 14. Clogging in-the'opening 11,

in the bottom of the tank 1, is removed or prevented by an air or water jet introduced through the pipe 18. 19 is a launder into which the liquid may overflow and from which the floated products may be delivered into the trough 20. 22 isthe feed pipe for the fresh ore delivered to the hopper 7 to 86 be introduced into the tank for treatment.

23 are battles arranged to retard the circulatorymotion of the liquid in the tank. Any number of these baffles ma be fastened to the hoops 25, and the ba es suspended in 90 the liquid by the suspenders 26. The depth of the baffles in the liquid may be regulated by the bolts 29, arranged with the, suspen- 'ders 26. Similarly, it may 'be desirable to have baffles '28 in the lower part of the tank to facilltate the settling down of the waste shown by 2* which represents a perforated hood, and by 2 which represents a porous hood. If perforations are used, the hood is rotated more rapidly than when a porous hood is used, for theporous material itself will helpto finely subdivide, or. atomize, the

air in its passage through the hood into the liquid in the tank. The speed of rotation may vary greatly, depending on whether a perforated or a porous hood is used: the nature of the material and the results desired For small machines it may vary from several hundred to several thousand revolutions per minute: for large machines it will be considerably less.

' rotated much more rapidly than porous hoods.

" ings.

The height of the hood or depth in the liquid may also vary greatly, and the pressure of the gas will be determined by the hydrostatic head of the liquid in the tank above the hood. Rapid rotation of the hood will tend to generate a more positive electrostatic action, through frictional electricand thus assist in getting leaner tail- It is preferred to have the surface of the hood quite smooth so thatrapid rota-- tion of the hood in the liquid will not consume excessive power.

In addition to the static electricity which is inevitably generated by the rapid rotaity,

tion of the hood throughthe liquid, it may at times be-desirable to pass an electric current through the liquid. This is readily accomplished by having one of the electric brushes acting on the shaft, designatedby 32, and the other at the Suspender bolts 29. The current will then pass through the shaft and hood, across the liquid, to thebaffle" plates 23, and out through the terminal 33.

The operation of the apparatus will now be described when used in the treatment of suitable ores. The tank 1 is filled with water or-ore sludge. The hood 2 is rapidly rotated by the pulley 6. The valve 10 is then opened and air or other gas under pressure forced into the hood through the pipe I 8, supplied'by the pipe 9, and regulated by the valve 10. The gas so forced into the hood will displace a certain amount of liquid in the hood and escape through the perforations 3 or the porous material 3 but in escaping through the hood into the liquid in the tank, thegas is atomized, or finely subdivided, in contact'with'the liquid. The

speed at which the hood is rotated will vary ace rding to its size and the material treated: for small hoods it will usually be greater than for large ones. The idea in operating the apparatus, is to get the gas in a'fine state of subd'vision. The finer the subdivision, the more effective the application of the'gas becomes, but this again may vary according to the material treated.

The hood may vary in details of construction, but for the purpose of the present description the idea is to have the surfaceof I the hood quite smooth, so as not to agitate the liquid any more than is unavoidable, and to useas little power as possible. The

.hood, primarily, is not intended as an agitator but rather as an atomizer, as the pre- Perforated hoods will be.

ferred method of operation. The result will be that while the liquid in the vicinity of .the hood has a tendency to circulate quite rapidly, this isobviated bythe baffles 23,-sothat the liquid in the upper-part of the tank will not be greatly disturbed and gives excellent conditions for the flotation froth to; separate from the gangue and rise to the surface of the liquid,

The ore, crushed to a suitable degree of fineness, usually'fromv 60 to 80 mesh, and treated with suitable frothing agents to facilitate flotation, such as oil, and possibly acid, is then introduced into the apparatus through the hopper 7, and, passing down through the stationary tube 2% in the hollow shaft 43 is delivered to the openings 35 and passes into the liquid in the tank through the rotatingpipe 30'or over the rotating surface 31. The more easily floatable particles will at once fioat, while the bulk of the ore will pass downwardly through the ascending bubbles, which will cause more particles to float. The liquid in the immediate vicinity of the shaft is not so much disturbed as that nearer the periphery of the hood, or ofthetank, and there is less air. The oreworking its way downwardly,

lands on the surface of the hood near the shaft and then, due to the rotation of the hood, is gradually worked toward'the periphery, where the action of the rotation and v the action of the air is more violent and floats the remaining floatable particles. The gangue passes down between the hood and the tank and finally "lands in the hopthe rotating pipe 30, or by the projecting surface 31, either by their action on the liquid itself, or indlrectly, by air currents induced by the rotating shaft and accessory or surface which also acts as. vanes. I

I The liquid in the upper part of the tank 1 may be made more quiescent by placing a to another similar ap-' coarse wire screen 36 on top-of the baflies 23,

but this will not ordinarily be necessary or desirable.

The gas in the hood is to a large extent self-regulating. ,The hood acts to a greater or less extent as a gas storage, or reservoir:

if the'hood becomes pretty well filled so that there is danger...of the-gas escaping at the bottom, the increased hydrostatic pressure will tend to force the gas out more rapidly so that once the conditions are established for a certain depth of hood and the size of perforations near the shaft fewer in numher, as well as smaller, than those nearer the periphery.

It will be observed that there is no mechanical connection between the rotating hood and the pipe 8 through which the gas is introduced into the hood. This is the preferred arrangement, for with a high rotary speed moving connections, such for example as when the gas is introduced through I a hollow shaft, are exceedingly troublesome.

The gas, introduced through the-mouth of the hood, offers no mechanical trouble of any kind, no matter what the speed of rotation may be.

With high rotary speeds the tube 24- in the hollow shaft 45 appears to be necessary:

with slow rotary speeds the tube 24 may be omitted. The size of the perforations in the hood is preferably varied, from small holes, say

inch, near the shaft, to, say inch near the periphery, but the best conditions can only be obtained by actual experimenting. The holes are preferably made larger than the material to be treated so as to preventthe material from clogging the holes, if the gas is passed through perforations.

In operating the apparatus probably the best results are obtained by having several of them in series, and passing the gangue from one apparatus into the next. In such cases it is desirable to vary the conditions of operation, especially the speed of rotation and the submergence of the hood in the liquid.

It is not likely that any floatable mineral Will get into the hood and causetrouble after the intense action the material has been subjected to in the uppenpart of the tank, but if any floatable mineral gets into the hood, it may be removed through-the pipe 34. If a perforated hood is used, the

idea would be to have the perforations large enough so that any floatable mineral, or even gangue, that got into the hood would pass through the perforations without obstructing them. If a certain amount of liquid is passed through the perforations with the gas that will do no harm. The apparatus is not sensitive in that respect.

In the preferred arrangement, as shown in the drawings, there is no mechanical connection between the gas pipe and the hood,

and the gas escapes through the gas passages in the hood into the liquid in the tank by means of its own buoyancy, and the gas,once having been delivered into the tank, isno longer under the direct pressure from the source of gas supply.

I claimz 1. In apparatus for treating li uids with gases, a tank adapted to contain t e iquid, a rotary member journaledon a substantially vertical axis submerged in the liquid,

stationary members in proximity to the r0-' tary member, and means for passing an electric currentfrom the rotary member to the stationary members.

2. In apparatus for treating liquids with gases, a tank adapted to contain the liquid, a rotary member journaled on a substantially vertical axis submerged in the liquid, stationary members in proximity to the rotary member, means for passing an electric current from the rotary member to the stationary members, and means for introducing the material to be treated in the upper portion-"of the tank and allowing it to descend through the zone of electrification.

WILLIAM E. GREENAWALT. Witnesses i FRED L. SCO'I'I, IVA L. MYERS.

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