US1732893A - Ore-flotation apparatus and method - Google Patents

Description

Oct. 22, 1929.

H. D. HUNT 1,732,893

ORE FLOTATION APPARATUS AND METHOD Filed Aug. 192'? 2 Sheets-Sheet l Svwemtoz A li/W 3331;; lul (lttozmmf v v Patented Oct. 32,1929

HARRY D. HUN'1, OF MIAMI, ARIZONA ORE-FLOTATION APPARATUS AND METHOD Application filed August 6, 1927. Serial 110,211,059.

v This invention pertains to ore flotation ap paratus and methodin which pulp formed by mixing finely pulverized ore wlth water and necessary flotation reagents is treated by the .passage ofair through it so as to cause a froth of air bubbles to be formed on the surface of the pulp. The bubbles carry in suspension a high percentage of the crushed min eral particles, which are carried off with the froth and subsequently recovered therefrom by suitable processes.

In the present invention air under pressure is admitted to the bottom ofthe' pulp and rises therethrough. This has been done by previous inventors, and that part of the process is not claimed as new. My invention pertains particularl to the treatment of the pulp after the injecte air has set the mass in circulation in the'flotation cell.

In some previous designs of apparatus for the same purpose the operation is very inefficientbecause the air serves simply to agitate the pulp, thereby forming only a thin layer of dense, heavily laden froth which, because of lack of supporting aeration, must be re moved promptly from the cell. On account.

of the thinness of the froth layer in this type of cell the pulp level must be kept close to the overflow lip with resultant danger of pulp so slopping over into the concentrate launder.

Another type of cell has an air lift with an air pressure chamber above the deflecting cap of the airlift. The purpose of the pressure chamber is to build up sufficient pressure in a the air compartment to cause the pulp ,dis-

charged from the air lift to pass beneath baffles into the froth compartments. As a re sult of this construction much of the air used in the air lift is carried beneath the baflies into'the spitakasten without being finely disseminated or emulsified, thereby causing considerable agitation in the spitzkasten, thus not only preventing the formation of new froth but also tending to break down the fragile bubble column already formed. In order to prevent such action it is necessary to provide a cascading discharge ofithe pulp from beneath underneath th; baflles into the froth compartments.

lift only to circulate the pulp and discharge a comparatively small quantity of froth on the top surface of the pulp in the cell. This does not produce a bubble column froth flotation result, but only a surface" tension flotation effect which has been found inadequate for the intended purpose. a The present invention is designed to overcome the defects and shortcomings of the above and similar processes .by providing a cell which operates with true bubble column action and produces a deep bubble column in a wide flotation cell. i The principal object of the present invention is to bring about an extremely fine subdivision :and dispersion of a large quantitj of air in thepulpwithout the use of any po- 'rous medium, and-to produce a typical bubble column froth flotation process. To accompl shthisresult the invention provides for the rlse of pulp and air at high velocity in the air lift compartment; for rapid circulatlon of pulp between the air lift and froth compartment; for cascade action. in dischargmg pulp frombeneath the deflector through an air space; for means permitting adjustment of the size and veloclty of the cascade; so for baifles adj ust-able to ermit only air in extremely finely subdivi ed condition to pass 1nto the froth compartment, thereby reducing agitation in the froth compartment to a minimum; for extremely fine division of the air prises the novel features an combinations of elements hereinafter describedand shown in the drawings, which by way of illustra- I th d fl t ap nd a free exlt'to the air fo ction show what I now consider to be the preall large bubbles from the air lift and to perto unit only fine'froth-forming bubbles to pass ferred form of the invention.

In the draw- Another type of flotation cell uses an air a Fig. 1 is a cross-section of the cell in operation, on the line 11 of Fig. 3.

Fig. 2 is a plan view of the cell. Fig. 3 is a side view of Fig. 2 partly broken 5 away to show the'interior construction.

Fig. 4 is an enlarged detail view on the line 4-4 of Fig. 3, showing the adjustable baflle supports.

In its essential features the cell comprises a receptacle 10, into the lower portion of which air is introduced through a row of drop pipes 12 projecting downwardly from the header 14,- to which air is supplied under pressure through pipe 16 provided with a regulating valve 18.

Extending lengthwise of the cell on bot-h sides of the drop pipes are plates 20 forming an air lift compartment 22 through which rises the air discharged from the open lower ends of the drop pipes.

I The receptacle is normally filled with pulp to the level indicated by line 24and the large bubbles of air which emerge from the drop pipes rise through the air lift compartment and set up a rapid upward circulation of pulp through the air lift compartment, drawing pulp from the cell and. discharging it against the'under side of deflector cap 26 which is adjustably supported on pipes 12 by set screws 28.. The purpose of this adjustment is to control the thickness, velocity and directional flow of the cascade. The ore pulp is directed by deflector 26 downwardly oven the tops of plates 20 through the space between plates 20 and bailies 30 back into the.

- cell. Baflle plates 30 extend the full length of the cell and are adjustably secured to the ends thereof by brackets 32 which are bolted 1 to the vertically and horizontally slotted brackets 34 substantially as shown in Fig. 4 so that baflles 30 may be adjusted vertically,

horizontally, and angularly, relatively tolthe v is - f pulpis orced in the form of a cascade, re-

cell.

The space between plates 20 and 30 is occllpied b air through which the returning sulting;in considerable entrainment of air I 36'between plates 20 and 30.

by the cascade in addition to the air already contained in the falling pulp. The cascade action also results in considerable agitation in the pulp into which the cascade If all of this agitation were transmitted' to bubble column 40, which is a mass of bubbles somewhat similar to soap bubbles, the bubble column would be caused to collapse. The amount of agitation transmitted from 36 to 40 may be regulated by the position of the 7 adjustable baflles 30, which may be set. as

already described, to give the most advantageous results.

Bafiies 30 serve not only to form a compartment or air space through which the pulp passing over the tops of plates 20 may fall as a cascade, but also to protect the bubble colfalls at,

umn 40 from direct action of the cascade. At the head of the cascade, all air not sufliciently broken up to be entrained in the pul makes its escape to the air compartment an thence to the atmosphere as indicated by the arrows in spaces 42 provided between the upper edge of the battles 30 and the under side of lips 44 whichcform partof deflector 26.

The action of the cascade as it passes through the air space between plates 20 and 30 serves to entrain additional air in the falling pulp and to finely divide and emulsify that air. Any air not properly entertained and emulsified is liberated as the cascade falls into the pulp and is free to escape through outlet 42. As circulation continues, due to action of the air lift, the air emulsion formed by the above action asses underneath adj ustable baflles 30 and a ds to the volume of froth in the bubble column. The lower edge of this adjustable baflie should not be so deeply submerged as to interfere with the directional forceof the cascade in causing the froth-forming bubbles to pass thereunder and to maintain the bubble column formed in the zone of quiescence. The thickness and velocity of the cascade is adjustable, depending upon the location of deflector plate 26.

When the height of the bubble column rises above the level of weirs 46 the froth overflows into launders 48 to pass therefrom to the concentrate discharge outlets 50.

Raw pulp is supplied to chamber 52 on the 'end of the cell and passes therefrom into the cell through opening 54 provided therefor in the end of the cell. The tailings discharge takes place from the other end of the cell through opening 56 and over adjustable weir 58 to the tailings discharge 60.

The above apparatus and method of operation insure rapid circulation of pulp due to the air lift, cascading of the pulp through an air spae (freely open to the atmosphere) in the compartments formed by the adjustable baflles and the air lift compartment, violent impin ment f of the cascading stream of pulp irectly on the pulp surface in this compartment and a zone of quiescence in the cell, with the result that a wide, deep column of froth is formed in the cell.

Study of the above flotation process in a full size glass apparatus indicates that the distance through which'the cascading pulp falls from beneath the deflector cap to the pulp surface is of importance in producing efl'ective aeration in the cell. A fall of 8 or 10 inches has been found eflective. The amount'of aeration decreases as this distance is decreased until with onl 2 or 3 inches fall, aeration ceases entirely. e amount of aeration also depends on the volume and initial velocity of the cascading stream as it leaves the underside of the deflecting cap. The velocityof the stream of pulp at this point should be made as great as is consistent with the cir- "the outer surface of the cascading pulp comes in contact with the bafile. on the line where the baffle enters the pulp. The position of the descending cascading pulp as shown in the drawing has been found to give the best re sults, that is,-a dis tinct airs ace should remain between the outer sur ace of the dcscending stream and the adjustable baffle and between the inner surface of the descending stream and the wall -of the air lift compartment. These air spaces should be freely open to the atmosphere through passages sufficiently large to insure that the air in the air spaces is under. atmospheric pressure "only. It has. been found that if the air in these air spaces is at a pressure in excess of atmospheric pressure the fine dissemination of air in the ore pulp by the cascade action is-hindered or even entirely prevented, dependent upon the amount of excess air pressure present, and there 1s a tendency for coarse undisseminated air to escape from the air spaces beneath the adjustable baflies and into the outer part of the cell or zone of quiescence and thus serimeans-for injecting air into the pulp therein to maintain a rapid upward movement of the pulp therethrough to a height above the nor- ;mal pulp level, means at the top of said up-.

lift chamber for directing said circulating pulp substantially directly downwardly in an expanding cascade, through a compartment freel open to the atmosphere adjacent to said upli to impinge directly on the surface of the pulp in said compartment, whereby the pulp is effectively aerated with froth-forming bubbles and means for collecting and separating the froth. j V

3. In anore flotation apparatus, a recep-. tacle adapted to contain ore pulp and to col lect and separate'froth, an uplift chamberwithin said receptacle, projecting a substantial distance above the normal pulp level, a baflle spaced from said uplift chamber, adj ustable toward and away therefrom and proj ecting into the pulp, and defining a compartment freely open to the atmosphere, means for injecting air into the pulp in said uplift chamber te-maintain'a rapid upward move ment of the pulp therethrough to a substantial height above the normal pul means at the top ofsaid uplift cliamber for directing said circulating pulp substantially directly downwardly'through said compartment in expanding cascade formation onto the surface of the pulp in said compartment,

chamber, and for causing said cascade level and a ously interfere withor entirely prevent forwhereby the pulp is effectively aerated with I mation of a deep column of froth in the outer part of the cell.

It is to be understood that the invention is not limited to the specific apparatus and method herein illustrated and described but can be embodied in other forms without'de-v parture from its spirit as defined by the following claims.

ll cla'im a 1. In an ore flotation apparatus, a rbceptacle adapted to contain ore pulp and to collect and separate froth, an uplift chamber within said receptacle, projecting a substantial distance above the normal pulp level,

' means for injecting air into the pulp therein to maintain a rapid upward movement of the pulp within said uplift chamber, ineans at the top of said uplift chamber for directing said circulating pulp substantially directly downwardly in an expanding cascade, throughfian air space freely open to the atmosphere, and for causing said cascade to impinge directly on the surface of thepulp, whereby the pulp; is effectively aerated with froth-forming bub- I bles, and means for directing the aerated pulpunder the pulp level 'of the froth chamher to exclude large bubbles.-

"-2. In more flotation apparatus, a rece tacle adapted to containorepulp, and, to collect'and separate froth, an uplift chamber within said receptacle, projecting a substantial distance above the normal pulp level,

froth-formingbubbles, and means for collecting and separating the froth.

4. In an oreflotation apparatus, a recep 1 to maintain a rapi upward movement of the pulp therethrough to aheight above the normal pulp level, means forming a compartment outsidethe chamber and freely open to the air, means at the top of said uplift cham- 'ber for directing said circulating pulp di ,rectly and substantially downwardly through said compartment in cascade formation, said means being adjustable for varying the size and velocity of said cascade, and for causing said cascade to impinge directly on the surface of the pulp in said compartment, vvhereby the pulp is effectively aerated with froth-forming bubbles, and

-means for collecting and separating the froth.

5. 1L method of treating ore pulp by the flotation process comprislng injecting air into a portion of o'repulp in an uplift chamher to cause a'rapid upward movement of pulp therethrough to a substantial height above the normal pulp level in a receptacle adjacent to said uplift chamber, and then projecting the moving pulp in expanding cascade formation Substantially directl downwardly froth-forming bubbles, while confining any large non-froth-forming bubbles to said partially isolated portion of the pulp.

6. A method of treating ore pulp by the flotation process comprising injecting air into a portion of ore pulp in an uplift chamber to cause a rapid upward movement of pulp therethrough to-a substantial height above the normalpulp level in a compartment ad-, jacent to said uplift chamber, and then projectin the movin pulp in expanding cascade ormation su stantially directly downwardly upon the surface of the pulp that is in this adjacent compartment, and so regulating the rate of discharge of said moving pulp from the ,uplift chamber and the distance through which the pulp is permitted to fall in cascade. as to insure that the moving pulp will attain a velocity at the point of its 1m lngement upon the surface of a partially iso ated portion of the pulp sufiicient to promote effective aeration of the pulp with frothforming bubbles and the transference of these froth-forming bubbles to the main body of the pulp in a zone vof relative quiescence and exclude the large non-froth-formin bubbles, whereby a wide deep column 0 froth is formed. e f v 7 A method of treating ore pulp by the flotation process comprising injecting air into a portion of ore pulp in an uplift chamber to cause a rapid upward movement of pulp therethrough to a substantial height above the 4 normal pulp level in a compartment adjacent to said uphftchamber, and then,projecting. the moving pulp in expanding cascade forma-. tion directly upon thesurface of that portion of the pul in this adjacent compartment,- and so regulating the rate of discharge of said moving pulp from the uplift chamber and the distance through which'the pulp is permitted I to fall in cascade as to insure that the moving pulp will attain a velocity at the point of its impingement upon the surface of a partially isolated portion of the pulp suflicient to promote effective aeration of the pulp with frothforming bubbles and the transference of these froth-forming bubbles to the main body of the'pulp in a zone of relative quiescence and excluding the large non-froth-forming bub- I bles, whereby a wide deep column of froth is formed, and permitting free ingress and egress of air from said adjacent compartment tothe atmosphere.

8'. In an ore flotation apparatus, a recep-, tacle adapted. to contain ore pul an uplift chamber within said receptacle, a afile spaced from said uplift chamber and depending beneath the normal pulp level in said receptacle, means for injecting 'air into the pulp in said uplift chamber to maintain a rapid upward movement of pulp therethrough to a substantial height above the normal pulp level and means at the top of said uplift chamber for directing said circulating pulp downwardly through said compartment in cascade formation and in direct impingement upon the surface of the ulp in said compartment, the outlet from' said uplift chamber being disposed at a suflicient elevation above the normal pulp level to insure that the descending cascade of pulp and air shall attain such a velocity at the point of impingement as to cause substantial entrainment of air therewith from the atmosphere through which it falls and to penetrate the body of pul sufiiciently to carry the frotlrfoiming bu bles present in, and formed by such cascade to be carried beneath the baffle and to rise through the main body of pulp in that portion of the receptacle beyond said baflie while the large non-froth-forming bubbles escape to the atmosphere from "the cascade compartment.

9. In an ore flotation apparatus, a receptacle adapted to contain ore pul an uplift chamber within said receptacle, a afile spaced from said uplift chamber, and projecting into the pulp, and defining a compartment freely open to the atmos here, means for injecting air into 'the upli t chamber to maintain arapid upward movement of pulp therethrough to asubstantial-height above the normalpulp .level,"and means at theto ofsaid upli chamber for directing the pu p downwardly through said compartment, in expanding cascade formation onto the surfaces of the p p in said compartment, the expandin cascade being slightly inclined toward the aflle,

whereby the pul is effectively aerated with froth-forming bu bles, and means for collecting and separating the froth.

10. A method of treating ore pulp by the flotation process comprising injecting air into 'a portion of ore pulp in an uplift chamber to cause a rapid upward movement of pulp therethrough to a substantial height above the normal pulp level in a compartment adjacent to said uplift chamber, and then projectin the moving pulp downwardly in an expan mg casca e andso regulating the dischar e of said moving pullp rom the u lift cham r and the distance t rough whic the pulp is permitted to .fall in cascade as to insure that'the moving which has a sli ht outward in-' 'clination upon the surface 0 that portion of the pulp that is in thisadjacent compartment mote effective aeration of the pulp with frothforming bubbles end the transference of these froth-forming" bubbles to the main body of the-pulp in a zone of relative quiescence and excluding the large non-froth-forming bfibbles, whereby a widevdeep column of froth is formed, and permittingfree ingress and egress of air from said adjacent compartment to the atmosphere. r f m In testimony whereof I hereto aflix my s'ignature. .7

HARRY D. HUNT.

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