US2002964A - Venturi flotation method - Google Patents

Description

May 28, 1935. w. L. SHEELER VENTURI FLOTATION METHOD Original Filed Jan. 23, 1930 INVENTOR m ll eon ,S'keeler W ATTORNEY Patented May 28, 1935 UNITED STATES PATENT F 2,002,964 FICE.

Walter Ron er, Vancouver, British 1 o bia, Canada Original application January 23, 1930, Serial No. 422,880, now Patent No. 1,916,020, dated June 27, 1933. Divided and this application May 20, 1931, Serlal-No. 538,740. In Canada August 28,

4 Claims.

The object of this invention is to provide a novel method of ore flotation and this case is divided out from my pending application filed January 23, 1930, Serial No. 422,880 patented 5 June 27, 1933, No. 1,916,020.

One of the features of this invention is to afford a large capacity, with a relatively low level of the solution,-and it is a feature of the invention to obtain prolonged duration contact of the ore values with the frothing agent and re-agents so as efiectivebr to clean and film or coat the ore values and facilitate collection of the latter by the bubbles in a plurality of stream paths of travel that are relatively short in length and which afiord passage for the solution for indefinite repeated treatment.

An important feature of the invention resides in a novel method of employing a gaseous agent, such for instance as air, to render the streams buoyantly ascendent and also cause an intensive diffusion of the gaseous agent with the ascendent streams, with an extremely low pressure of such agent, the latter functioning to effect ascension of the streams by creating a hydrostatic difierential in the pulp body favorable to said streams.

A further feature, in combination with the low pressure feature, resides in supplying such gaseous agent in extremely large volume for callsing ascension of the .bubble streams to thereby increase the content of gaseous agent supplied to each stream and hence correspondingly increase diffusion therein and accelerating the.

frothing, thereof.

It is a further feature of the invention to cause an acceleration of flow of the ascending bubble streams by constricting or contracting the latter and thereby breaking up the larger bubbles that may initially form therein, and in thus breaking up the larger bubbles, I thereby increase diffusion of the gaseous agent to a greater extent'than otherwise.

It is a fm'ther feature of the invention to slow up or retard the velocity of the ascending streams after they have been accelerated and'at the same timefreethestreamstoanexposuretoahnosphere to extended or expanded areas to increas ing frothing, and hence, while the streams are ascendlngx the change in velocity of the flow creates a differential that in itself not only serves to break up the larger bubbles but also increases diffusion of the gaseous agent throughout the streams. V 2

It is a further feature of the invention to restrain discharge of the goth emitted from said streams for mslight distance or extent to allow the froth cumulatively to build up while exposed to atmosphere, preferably above the solution level, and then cascade the froth down onto said level, this aeration being supplemental to that effected while the streams of the solution are ascending.

A further feature consists in releasing the cumulated froth at increasing elevations for cascading discharge down onto the solution level dependent upon the degree or volume of froth cu-' Fig. 1 is a transverse vertical sectional view on line ll of Fig. 2, illustrating a flotation cell capable of performing the method of this invention.

Fig. 2 is a vertical sectional view, partly in elevation, of the cell shown in Fig. 1, and taken on line 2-2 of Fig. 1. I

Like characters of reference designate similar parts throughout the different figures of the drawing.

' The cell structure shown constitutes one form whereby this method can be carried out but this specific form of cell is not essential to my invention. However, as illustrated, the cell is formed of a bottom wall I, end walls 2 and 3 and side walls 4. Converging walls '5, extending longitudinally of the cell, may be anchored to the side walls 4, the ends walls 2 and 3, and to the bottom wall I, in any desired manner, and they function to guide the values and other solids in solution toward the longitudinal linear center of the cell as said material descends therein. I have indicated the solution level at 6, although this level may vary above or below the indicating line, and it will be further understood that this is the solution level, and not the froth level, as the latter, or froth, is superimposed on the solution level and attains a considerable height. While the solution level may, and doubtless will vary,

it is always shallow'in depth as it is a feature of this invention to operate under a shallow depth solution, the depth in actual practice being beheretofore been considered essential by reason' of the operation of certain features and means to be presentlydescribed.

The walls 4 extend above the converging walls 5 and the upper edges 1, form weirs over which tion level 6 and open to atmosphere and dis-.

the froth discharges that has accumulated on the solution level 6. Walls 8 and 9 form launders I0, into which the froth discharges.

An ingress chamber II, which may be fed in any desired manner, delivers to the cell through an ingress opening I2, the latter being located in end wall 2. An egress opening I3 in end wall 3, delivers to a discharge chamber I4 having a weir It, that may be adjusted by fillets I5 to adjust the overflow into an outlet chamber I6, from which an outlet pipe II, leads, as will now be clear to those skilled in this art.

Disposed in longitudinally alined and substantially horizontal relation in the cell is a plurality of bubble stream forming pipes I8, all of which are alike in structure and operation and hence only one thereof need be described in detail. The lower open ingress ends I9, of these pipes, are shown immersed in the pulp solution and the upper egress ends of said pipes, as indicated at 20, are disposed slightly above the indicated solucharge into or onto the pulp solution in the cell, or theretoward. In the preferred construction, these strearfiforming pipes are in the shape of venturi, the ends I9 and 20 being relatively and sufliciently enlarged with respect to their central portions 2|, which form the constrictions of the venturi. It may be stated that the venturi dimensions of these pipes may vary widely, in practice, to meet varying conditions, and the venturi form is merely outlined.

While it is practical to rely upon the lower ingross ends I9, still, I have shown an ingress channel comprising walls 22 and 23, which may be suitably anchored to the end walls 2 and 3 and serving to support the pipes I8. The channel form is created by a top wall 24, on which the pipes I8 directly rest and which is provided with openings 25 in position to register with the various pipes I8. The walls 22 and 23, advantageously diverge, as shown, and hence the venturi function may be said to begin with the restriction of said walls although by reason of the fact that these walls are a continuous open channel, the actual andeifective restriction would reside at 2|.

Above the pipes I8 is what I will term a restricted froth expansion chamber or channel which is formed by a wall 26, having openings 26', one for the egress end of each pipe I8, and diverging walls 21, extending upwardly from the egress ends of pipes I8 and suitably anchored to the end walls 2 and 3. This expansion chamber might terminate the upper portion of the structure and would be clearly operative if the froth could pass over its walls 21, down onto the solution level as the froth built up in said chamber. However, under some conditions, it is desirable to afford additional restraint for the froth to further subject the latter to aeration by exposure to atmosphere, as I will now describe.

ther, the delivery ends 35 are disposed in alined relation so that gaseous streams are delivered in opposed relation to cause the emitting streams to collide and thereby break up and tend to prevent the formation of large bubbles. While in actual practice, this colliding delivery has certain advantages, I find that it is not essential, and hence the delivery ends of the pipes may be otherwise disposed. A valve 36, is provided for each pipe 34, to control the rate of flow of the gaseous agent to the respective venturi I8, individually.

With this type of cell, I have carried on effec-' tive operation with a supply of air as low as eleven ounces per square inch, including skin friction developed in transmission through the pipes, and of course this pressure minimum could be still further reduced if transmission loss could be lowered, and hence, the effective pressure at the ends 35, was in fact, less than eleven ounces.

It will now be clear that while the ends 35 I could deliver directly to the ingress ends I9 of the venturi I8, still, the provision of the ingress chamber formed by walls 22 to 24 insures less loss of air that might escape laterally of the venturi unless the ends of the latter were flared to a considerable extent more than shown, which is clearly possible and practical.

However, the essential features to the very best results, is the combination of low pressure and large volume of the gaseous agent, in combination with a shallow depth of solution, and these are the conditions under which I have obtained results in actual installations of the greatest value, and economy.

A special feature of importance is that a venturi will only function effectively within certain fixed or relatively fixed limitations in height, the variations in diameter having a wider range or latitude, and in adapting the venturi to a shallow depth cell, I have combined a venturi in a functional association in which it is best adapted to operate with a maximum efiiciency.

The operation will possibly be clear from the forgoing but it may be generally recapitulated as follows:-- r

After the cell has been charged so that a solution level indicated at 6, or approximately that elevation has been established, the gaseous agent supplied to the pipes I8 creates a hydrostatic differential favorable to said pipes I8, which are preferably although not wholly essentially of the venturi type, and'the streams formed in said pipes with the solution at' the level indicated, become buoyantly ascendent, and they rise in the pipes I8 and are delivered in the form of froth back to the solution, portions not frothed being of course returned back to the pipes,

Thus, it will be seen that portions of the solu-- tion can repeatedly pass upwardly through any one or more of the pipes I8, and it is because of this fact, together with the fact that I employ a plurality of pipes I8, that I obtain such a prolonged and intensive duration contact of the values with the re-agents, and achieve such a high, degree of recovery. Therefore, it will now be clear that even if the actual path of travel upwardly through one pipe l8, and its constituent parts, is relatively short, as compared with a cell having a solution depth of six feet for instance, the repeated treatment not only afiords therequisite duration of contact but it also compensates for the shallow depth which latter otherwise would constitute a distinct limit of capacity.

Now as the large volume of the gaseous agent, whatever it may be, ascends into the ingress ends of the venturi l8, it has a tendency to form relatively large bubbles, and it is well known that smaller bubbles ail'ordthe greatestrecovery of values. 'However, even if the bubbles initially formed are relatively large, the constriction 2| will reduce the bulk passing through the venturi and this serves to break up the larger bubbles which almost instantly reform into smaller bubbles thereby causing an intensive diffusion of air throughout the mass which results in a preliminary and very effective aeration.

After the solution ascends above the construction 2!, it is permitted to expand to atmosphere and this intensifies and increases frothing and aeration as a multitude of very small bubbles will form just as soon as the solution is exposed to atmosphere.

At this point it is desired to emphasize the duel capacity of the pipes It, in the event that they are made in the venturi form, and that is, the acceleration that the lower section below the constriction 2| aifords in increasing the ascending yelocity of the solution, and the subsequent retardation aflorded by the flaring egress portions of pipes l8, results in a flow differential that causes a most intimate and thorough diffusion of the gaseous agent throughout the ascending solution, while the latter is rising in pipes [8.

It will be clear that the venturi pipes form annular upright streams which are annular throughout their length while in said pipes, and that frothing actionstarts in said pipes and discharge of the froth is in unrestrained bulk flow over the louvres. It will further be noted that ascent of the ore pulp streams results not only from venturi action but also from the buoyancy caused by the gaseous medium fed thereto.

It is believed that the hereindescribed method will be clearly understood from the foregoing description, and it will be understood that I do not wish to be limited thereto except for such limitations as the claims may import.

I claim:

1. A shallow depth and low pressure venturi mineral flotation method, which comprises, forming from the pulp body a plurality of separate short upright and laterally confined annular streams of the pulp solution opening from said pulp body to prolong contact of the solid values with the re-agent and frothing agent, and each stream discharging above and down onto said pulp body in unrestricted bulk flow in permeating said streams with a gaseous agent at low pressure and in sufliciently large volume to render said streams ascendentlybuoyant and form mineral collecting bubbles therein as said streams ascend, in annularly constricting the ascending streams at a given elevation below the point of discharge of said streams onto said D1111 body to break up large bubbles and accelerate the rate of flow and thereafter expanding said streams in exposure to atmosphere to froth the same and slow up the rate of ascending flow, by venturi action, whereby the resulting differential of flow will diffuse the gaseous agent through said streams and break up the larger bubbles 2. A low pressure shallow depth mineral flotation venturi method, which. comprises, forming from a pulp body a plurality of separate independent upright annular streams of the pulp solution each stream discharging above and down onto said pulp body to thereby intensify and prolong contact of the solid values with the re-agent and frothing agent, in permeating said annular streams with a gaseous agent at low pressure and sufficiently large volume to initiate and sustain venturi action and render said annular streams ascendantly buoyant and form mineral collecting bubbles therein as said streams ascend, in

accelerating the ascent of said annular streams to a given point of elevation with respect to the solution level, and in thereafter reducing the velocity of ascent and expanding said annular streams to atmosphere to cause said streams cumulativeLv to froth and build up above and then descend down onto the solution level in unrestrained bulk flow.

3. A low pressure shallow depth mineral flotation venturi method, which comprises, forming from the pulp body a plurality of independent and laterally confined annular streams of pulp solution, in permeating each stream with a gaseous agent sufficiently to initiate and sustain venturi action and render said annular streams ascendently buoyant and form collecting bubbles therein as said streams ascend, in annularly constricting said streams to accelerate ascent thereof to a given point of elevation, and in thereafter expanding said annular streams and slowing their velocity and exposing the expanded streams to atmosphere to cause the expanded streams cumulatively to froth to an elevation above the pulp level, and in cascading upper portions of the cumulated froth down onto the pulp level in unrestrained bulk to increase froth formation.

4. A shallow depth low pressure venturi mineral flotation method, which comprises, forming from a pulp body a short upright and laterally confined stream of the pulp solution ingressing from the pulp body to prolong contact of the solid values with the reagent and frothing agent and the stream discharging above and down onto the pulp body in unrestrained bulk flow, in permeating saidstream with a gaseous agent at low pressm'e and in sufllciently large volume to render the stream ascendently buoyant and form mineral collecting bubbles therein as .said stream ascends, in annularly constricting the ascending stream at a given elevation below the point of discharge of said stream onto said pulp body, to break up large bubbles and accelerate the rate of ascending flow and thereafter expanding said stream in exposure to atmosphere to froth the same and slow up the rate of ascending flow, whereby the resulting differential of flow will diffuse the gaseous agent through said stream and break up the larger bubbles.

WALTER LEON SW.

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