US3371779A - Concentration of minerals - Google Patents

Description

March 5, 1968 c. A. HOLLINGSWORTH ETAL 3, 9

CONCENTRATION OF MINERALS 5 Sheets-Sheet 1 Filed June 24, 1965 BO EKMOZD mum- INVENTORS Clinron A.Hollingsworfh LSopp BY Bobby March 5, 1968 c. A. HOLLINGSWORTH ETAL 3,

CONCENTRATION OF MINERALS Filed June 24, 1965 5 Sheets-Sheet 2 FIG. 5

OVERFLOW 75 le 2s I I I I I I I f I I 5| I s 82 z 83 I I I I I I I v UNDERFLOW I I u 5 1' WATER 7 REAGENTS INVENTORS 53 Clinton A. Hollingsworfh a 48 BY B y S pp ATTOF'QN I s March 5, 1968 c. A. HOLLINGSWORTH ETAL 3,

CONCENTRATION OF MINERALS 5 Sheets-Sheet 3 Filed June 24, 1965 w. \1 E m mwT INVENTORS Climon A. Hollingsworrh BY BObb Supp A TT Z) R Y March 5, 1968 c. A. HOLLINGSWORTH ETAL 3,371,779

CONCENTRATION OF MINERALS 5 Sheets-Sheet 4 Filed June 24, 1965 BOJmKMOZD BOJHEMQZD h D. Hm 0 MW m 1 N .m y/fl A w :5 mo E I n Y 09 m a .m U

March 5, 1968 c. A. HOLLINGSWORTH ETAL 3, ,7

CONCENTRATION OF MINERALS 5 Sheets-Sheet 5 Filed June 24, 1965 |65\ Im I j I I58 I49 INVENTORS Clinton A. Hollingsworfh United States Patent 3,371,779 CONCENTRATION OF MINERALS Clinton A. Hollingswortll, Lakeland, and Bobby L. Sapp, Plant City, Fla., assignors to The Borden Company, New York, N.Y., a corporation of New Jersey Filed June 24, 1965, Ser. No. 466,546 23 Claims. (Cl. 209-166) ABSTRACT OF THE DISCLOSURE The invention relates to the concentration and beneficiation of minerals and other particulate matter by froth flotation, more particularly to a novel hydraulic-pneumatic flotation apparatus and to a novel method of froth flotation by the dispersion of aerated water in a hydraulic compartment and its uniform distribution through a constriction plate into a flotation chamber.

Commercially valuable minerals, for example, metal sulfides, apatitic phosphates and the like, are commonly found in nature mixed with relatively large quantities of unwanted gangue materials, and as a consequence it is usually necessary to beneficiate the ores in order to concentrate the mineral content thereof. Mixtures of finely divided mineral particles and finely divided gangue particles can be separated and a mineral concentrate obtained therefrom by well known froth flotation techniques. Broadly speaking, froth flotation involves conditioning an aqueous slurry or pulp of the mixture of mineral and gangue particles with one or more flotation reagents which will promote flotation of either the mineral or the gangue constituents of the pulp when the pulp is aerated. The conditioned pulp is aerated by introducing into the pulp a plurality of minute air bubbles which tend to become attached either to the mineral particles or to the gangue particles of the pulp, thereby causing these particles torise to the surface of the body of pulp and form thereat a float fraction which overflows or is withdrawn from the flotation apparatus.

In conventional sub-aeration flotation machines the aqueous pulp ordinarily is aerated by means of a mechanical impeller-type agitator and aerator which extends into the body of pulp and which disperses minute bubbles of air throughout the body of pulp by vigorous mechanical agitation of the pulp. Flotation machines which employ vigorous agitation of the pulp to effect aeration thereof possess serious disadvantages when employed in connection with pulps that contain difiicult to float particles which, because of the vigorous agitation, may not become attached to a suflicient number of air bubbles to float the particle or which may be dislodged from the froth column lying on top of the agitated body of pulp. Moreover, uhen used in connection with pulps containing soft or friable particles, vigorous mechanical agitation of the pulp tends to produce slimes which in many cases adversely affect the efliciency of flotation otherwise obtainable.

To overcome these and other disadvantages of mechanically agitated flotation machines it has heretofore been proposed that aerating air be introduced directly into a relatively quiescent body of aqueous pulp by means of air dilfusers or aerators which are immersed in or are in direct contact with the pulp. Such flotation apparatus, which are commonly referred to as pneumatic flotation machines, have been found to be very eflicient when used with ores that do not require vigorous agitation in order to prevent too rapid settling out of the solid particulate matter in the aqueous pulp, and they are particularly useful when the pulp being treated tends to form harmful slimes when subjected to vigorous agita- ICC tion. The air diffusers or aerators of conventional pneumatic flotation machines ordinarily comprise a porous mateminute bubbles of aerating air are directly introduced into the aqueous flotation pulp. As a consequence, convention-al pneumatic flotation machines are subject to a very troublesome problem caused by the tendency of the air diffusers immersed in or in contact with the pulp to become covered with a tenacious coating composed of oily flotation reagents and fine particles of minerals and gangue which clogs the minute openings through which air is introduced into the pulp by the air diffusers.

The clogging of the minute openings of the air diifusers causes uneven distribution of aerating air throughout the body of aqueous pulp in the flotation machines. Moreover, pneumatic flotation machines heretofore known in the art possess other shortcomings that adversely affect their efficiency when such machines are enlarged in size and capacity for use in large scale commercial operations.

Among the more troublesome of these shortcomings is the tendency of the rising column of air bubbles to become channelized and thereby unevenly areate the aqueous pulp. In addition, the entrainment of non-float particles in the overflow fraction withdrawn from the machine,

and the disruption of the desired quiescent condition I of the aqueous pulp caused by the withdrawal of the underflow fraction near the bottom of the machine also cause operational problems.

contact with the aqueous pulp, the pulp being aerated by introducing thereinto pro-aerated water from a hydraulic compartment disposed below the main flotation compartment of the machine. Moreover, we have developed a new pneumatic flotation machine embodying this discovery in which pre-aerated water is introduced into the flotation compartment from the hydraulic compartment therebelow through a plurality of suitable orifices formed in the bottom wall of the flotation compartment. Inaddition to this important improvement over the prior art practice, our new flotation process and the apparatus we have developed for carrying out this process embody a number of significant improvements in the manner of introducing the material into the machine, in the manner of minimizing entrainment of non-float particles in the float fraction, and in the manner of withdrawing the underflow fraction from the apparatus so as to avoid disruption of the desired quiescent condition of the pulp contained in the flotation compartment of the machine.

Specifically, our new process for concentrating minerals by froth flotation of an aqueous pulp containing a 1- mixture of mineral and gangue particles comprises first conditioning the aqueous pulp with at least one flotation reagent adapted to promote flotation of one of the types of particles (i.e., mineral or gangue particles) present in the aqueous pulp when the pulp is aerated. The conditioned pulp is introduced in a flotation compartment containing a relatively quiescent body of the aqueous pulp, and aerated water is introduced into the lower portion of the flotation compartment through orifices formed in the bottom wall of the flotation compartment. A body pulp in the lower portion of the flotation compartment through the aforementioned orifices formed in the bottom wall of the flotation compartment. The static pressure of the aerated water in the hydraulic compartment is maintained sufliciently higher than the static pressure of the aqueous pulp in the lower portion of the flotation compartment so that pre-aerated water is introduced into the lower portion of the flotation compartment as previously described and so that the flow of pulp from the flotation compartment into the hydraulic compartment through the aforementioned orifices is prevented. An overflow fraction containing floated particles of the pulp is withdrawn from the top of the body of aqueous pulp and an underflow or non-float fraction containing non-floated particles of the pulp is withdrawn from the pulp in the lower portion of the flotation compartment.

Our new flotation apparatus for effecting concentration of minerals by the separation of a mixture of mineral particles and gangue particles into a float fraction and anon-float fraction in accordance with our invention comprises a flotation compartment adapted to contain a substantially quiescent body of an aqueous pulp of the mixture of particulate material, feeding means adapted to introduce conditioned aqueous pulp into the flotation compartment, froth overflow means associated with the upper end of the flotation compartment for discharging therefrom the float fraction of the particulate material, and underflow discharge means associated with the lower end of the flotation compartment for withdrawing therefrom the non-float fraction of the particulate material. A hydraulic compartment is disposed below the flotation compartment and is separated therefrom by a constriction plate, the constriction plate comprising the bottom wall of the flotation compartment and being formed with a plurality of geometrically spaced openings or orifices adapted to permit aerated water to flow therethrough. The hydraulic compartment is adapted to contain a body of water maintained at a slightly higher pressure than the pressure of the pulp in the flotation compartment immediately thereabove so that aerated water will flow from the hydraulic compartment into the flotation compartment and so that the flow of pulp through the constriction plate into the hydraulic compartment will be prevented. Means are provided for introducing water and for introducing air into the hydraulic compartment, and aerator means are provided for forming an intimate dispersion of fine air bubbles throughout the water in the hydraulic compartment.

In the preferred embodiment of our flotation apparatus the pulp feed means is provided with a novel hydraulic mixing device, hereinafter more fully described, that gently and intimately mixes the initial feed material with additional water, and optionally with flotation reagents, to obtain a conditioned pulp having the desired content of solids and reagents that is then introduced directly into the flotation compartment. A froth cleaner compartm'ent is advantageously disposed immediately adjacent the froth overflow means of the flotation compartment so as to permit non-float particles entrained in the froth column to drop therefrom and be returned to the main body of pulp in the flotation compartment. The underflow discharge means for the non-float fraction of the pulp preferably is specifically designed to discharge a relatively large quantity of pulp underflow at a relatively low linear velocity so as to reduce disruption of the desired relatively quiescent condition of the body of pulp in the flotation compartment and thereby prevent removal with the underflow of float particles that chance to be in the lower portion of the flotation compartment.

The removal of the air diffusers from direct contact with the aqueous pulp in the flotation compartment, and the provision of a separate hydraulic compartment in fluid communication with the lower portion of the flotation compartment and containing a body of aerated water substantially free of the aqueous pulp, completely eliminate the clogging of the minute openings in the air diffusers which heretofore was the cause of so many operating difliculties. In addition to the avoidance of the aforementioned operating difficulties, the use of our new process and of our new flotation apparatus for carrying out the process makes possible substantial improvements in the efliciency of separation and concentration of mineral particles. For example, we have found that the flotation efficiency (that is, the increase in grade of mineral concentrate obtained and the percentage recovery of the mineral achieved) of one flotation cell embodying our invention is commonly equivalent to the flotation efliciency of a series of three to six conventional sub-aeration flotation machines. Moreover, flotation apparatus embodying our invention not only is capable of beneficiating all those materials normally treated in conventional flotation machines but is also capable of beneficiating coarse materials that are normally treated by means of belts, tables and the like. Another important advantage of our new apparatus is that the apparatus has no moving parts in direct contact with the rather dense (up to 60% or more solids) and abrasive aqueous pulp in the flotation compartment, and as a consequence operating costs and in particular the cost of maintenance and repairs are substantially reduced. Other advantages of the process and apparatus of our invention will become evident from the ensuing detailed description thereof.

The unique advantages possessed by our new flotation process and, in particular, the hydraulic-pneumatic flotation apparatus we have developed to carry out the process, will be better understood from the following description thereof, in conjunction with the accompanying drawings of which:

FIG. 1 is a side elevation, partly in section, of an advantageous embodiment of our new flotation apparatus,

FIG. 2 is a plan view of the flotation apparatus shown in FIG. 1,

FIG. 3 is a sectional view of an advantageous form of water-jet aerator for simultaneously aerating and agitating the water in the hydraulic compartment of our new flotation apparatus,

FIG. 4 is a sectional view of the improved pulp feed mixer and distributor advantageously employed in connection with our new flotation apparatus,

FIG. 5 is a side elevation, partly in section, of a cylindrical flotation cell embodying significant features of our invention,

'FIG. 6 is an enlarged perspective view, partly broken away, of the froth cleaner compartment associated with the froth overflow means of our new flotation cell,

FIG. 7 is a side elevation, partly broken away, of another advantageous embodiment of our new flotation apparatus in which two flotation compartments are arranged side by side for horizontal flow of the aqueous pulp through the second flotation compartment,

FIG. 8 is a sectional view along line 8-8 of FIG. 7 of the two compartment flotation cell shown in FIG. 7,

FIG. 9 is a plan view of the two compartment flotation cell shown in FIG. 7,

FIG. 10 is a perspective view partly broken away of yet another advantageous modification of our new flotation apparatus in which a number of flotation compartpneumatic flotation apparatus shown in FIGS. 1 and -2 of the drawing is provided with a number of structural features which cooperate to obtain significantly improved flotation efficiencies when the apparatus is employed to carry out the separation of a variety of particulate mineral and gangue feed materials into the desired float and non-float fractions. The flotation apparatus embodying our invention comprises a flotation compartment adapted to contain a body of aqueous pulp to be separated into float and non-float fractions, a hydraulic cornpartment 11 disposed directly below the flotation compartment 1t] and adapted to contain a body of aerated water that is introduced into the flotation compartment through orifices 12 formed in the constriction plate 13- which serves as the bottom wall of the compartment 10. A combined pulp feed mixer and distributor 14 is pro' vided adjacent the upper end of the apparatus for introducing a conditioned aqueous pulp into the flotation compartment 14 of the apparatus. Weir-like froth overflow means 15 are also provided adjacent the upper end of the apparatus for withdrawing the float fraction (referred to as the rougher float) from the flotation compartment, the rougher float fraction being introduced onto an aqueous medium contained in a froth cleaner compartment 16 associated with the weir-like rougher float overflow means 15. The froth cleaner compartment 16 is provided with cleaner float overflow means 17 for withdrawing a cleaner float fraction from the apparatus. Low velocity underflow discharge means 18 is provided adjacent the lower end of the flotation compartment for withdrawing underflow or non-float material from the flotation compartment, and a pulp level control box 19 communicating with the flotation compartment is provided for control of the level of pulp in the flotation compartment. Air aspirating water-jet type air diffusers 2b are provided in the hydraulic compartment 11 for dispersing aerated water throughout this compartment.

In the embodiment of our invention shown in FIGS. 1 and 2, the flotation compartment 19 has a substantially rectangular cross section defined by the side Walls 22 and 23 and the end walls 24 and 25 of the apparatus, the constriction plate 13 serving, as previously noted, as the bottom wall of the flotation compartment 10. The hydraulic compartment 11 is defined by the constriction plate 13 which serves as the top wall thereof and by the lower portions of the side walls 22 and 23, the lower portions of the end walls 24 and 25, and the bottom wall 26 of the appartaus. The froth cleaner compartment 16 is defined by lateral extensions of the side walls 22 and 23, the upper portion of the end wall 24, the cleaner compartment outer wall 28, and the cleaner compartment slanted bottom wall 29, the upper portion of the outer wall 28 being slanted laterally away from the side wall 24 and terminating at its upper end wall in the adjustable, weir-like, cleaner float overflow means 17.

It is of fundamental importance in the practice of our invention that the hydraulic compartment contain a uniformly aerated body of water maintained at a slightly higher pressure than that of the aqueous pulp in the lower portion of the flotation compartment 10. Accordingly, the hydraulic compartment -11 is provided with means for introducing aerating air into the hydraulic compartment, with means for introducing water into the compartment, and with means for forming a uniform dispersion of minute air bubbles throughout the water in the compartment. The functions of the air introducing means, the water introducing means and the air dispersing means may each be carried out by separate devices or mechanisms. For example, water and air can be introduced through separate conduits or pipes into the hydraulic compartment in the immediate vicinity of a mechanically operated impeller-type agitator which intimately mixes the air in the water and distributes the aerated water throughout the hydraulic compartment. Advantageously, however, the functions of the air introducing means and the air dispersing means, and preferably the functions of all three of the aforesaid means, are carried out essentially simultaneously by a single device or mechanism which is referred to herein as an air diffuser, although the combined functions of the so-called air diffuser may be broader than this term implies. The air diffuser may he a conventional, mechanically driven air aspirating impeller-type device such as will be hereinafter more fully described, or, advantageously, it may be of the air aspirating water-jet type such as that shown in FIG. 3 of the drawing, and the air diffusers 20 employed in embodiment of our apparatus shown in FIGS. 1 and 2 are water-jet type devices.

An advantageous form of air aspirating water-jet air diffuser useful in the practice of our invention is shown in FIG. 3 of the drawing. The air difluser comprises a water-jet nozzle member 31, an air aspirating venturi member 32, a check valve member 33 and a coupling member 34 by which the water-jet air diffuser is con nected to the opening 35 formed in the bottom wall 26 of the hydraulic compartment 11. A jet of water directed into the venturi member 32 by the nozzle member 31 draws or aspirates air into the venturi member through the air inlet nipple 36 in the manner well known in the hydraulic art. The aspirated air becomes intimately dispersed throughout the water in the air diffuser as the mixture of air and water travel upwardly through the device into the hydraulic compartment. Water baffle members are provided in the hydraulic compartment 11 to insure that the stream of aerated water issuing from each air diffuser will become uniformly dispersed throughout the hydraulic compartment. The baffle members may take any appropriate form that insures uniform distribution of water throughout the hydraulic compartment. In the embodiment of our invention shown in FIG. 3 the baffle members associated with each air diffuser 20 comprise a vertically disposed cylindrical guide member 38 positioned on support rods 39 between the lower wall 26 and the constriction plate 13 (which serves as the upper wall of the hydraulic compartment) and a horizontally disposed circular deflection plate 40 positioned on support rods 41 between the cylindrical guide member 38 and the constriction plate 13 directly in the path of the stream of aerated water issuing from the air diffuser 20.

The stream of aerated water from the air diffuser 20 impinges against the horizontal deflection plate 40 and is deflected horizontally in all directions as indicated by the arrows in FIG. 3. The aerated water in the hydraulic compartment is kept in a state of vigorous agitation by the aforesaid horizontally deflected stream, and as a result of this vigorous agitation aerated water is maintained uniformly dispersed throughout the entire hydraulic compartment 11. As the pressure of the aerated water in the hydraulic compartment is maintained slightly higher than that of the aqueous pulp in the flotation compartment, a portion of the aerated water thus dispersed throughout the compartment 11 flows upwardly through the orifices 12 formed in the constriction plate 13 into the lower portion of the flotation compartment thereabove. The remainder of the aerated water circulates vigorously throughout the hydraulic compartment, a substantial portion thereof constantly being drawn into and impelled upwardly through the cylindrical guide member 38 where it is mixed with freshly aerated water issuing from the air diffuser 20, as also indicated by the arrows in FIG. 3.

As previously pointed out, it is important in the practice of our invention that the air diffusers 20 in the hydraulic compartment 11 be maintained substantially out of contact with, and, therefore, that the aerated water in the hydraulic compartment be maintained substantially free of, the solid particulate matter and oily flotation reagents present in the aqueous pulp contained in the flotation compartment 10. Accordingly, water and aerating air are introduced into the hydraulic compartment 11 through the air diffusers 20 at' a rate sufficient to insure that the static pressure of the aerated air in the hydraulic compartment is maintained appreciably above the static pressure of the aqueous pulp in the lower portion of the flotation compartment 10. Specifically, we have found that the pressure dilferential between the aerated water in the hydraulic compartment and the aqueous pul in the lower portion of the flotation compartment should not be permitted to fall below about 6.5 psi, and preferably not below about 1 psi, in order to maintain the hydraulic compartment substantially free of aqueous pulp, and we presently prefer to operate within the range of about 2 to 4 psi.

As Water and aerating air are introduced into the hydraulic compartment 11, a quantity of aerated water equal to the quantity of water and aerating air thus introduced exits from the hydraulic compartment through the orifices 12 formed in the constriction plate 13 in the form of a plurality of streams of uniformly aerated water. In this connection, it is important to note that the constriction plate 13 is not an air diffuser and that the orifices 12 formed therein are not intended to control air bubbles sipe or promote air diffusion, the stream of water flowing through each orifice 12 already being aerated with a multitude of minute, uniformly dispersed air bubbles. The orifices 12 formed in the construction plate 13 are relatively large and are distributed in a relatively widely spaced geometric pattern across the entire area of the constriction plate in order to insure uniform distribution of the aerated water being introduced into the flotation compartment, and, thereby, to insure uniform aeration of the aqueous pulp in the flotation compartment. By way of example, a typical constriction plate 13 is formed with orifices 7 inch in diameter spaced apart on 2 inch centers, as contrasted with the multitude of minute, bubble-forming pores with which an aerator of conventional design is formed.

In the interest of insuring uniform dstribution of aerating air throughout the hydraulic compartment 11, the hydraulic compartment may be divided into a number of smaller hydraulic compartment sections by suitable vertical partitions, each section being served by one or more air diffusers 20. Similarly, in the interest of insuring uniform distribution of aerating air in the flotation compartment 10, the flotation compartment may be divided by suitable vertical partitions into a number of smaller flotation compartment sections. if it is desired to increase the degree of aeration of the aqueous pulp in the flotation compartment, additional aerating air can be aspirated into each water-jet air diffuser 20 by increasing the flow of water through the water-jet air diffuser, or additional air can be introduced under pressure (for example, by means of a suitable blower) at the air inlet nipple 36 of the air diffuser 20.

The combined pulp feed mixer and distributor 14 (hereinafter referred to as the feed means 14) of the embodiment of our new flotation apparatus shown in FIGS. 1 and 2 is shown in somewhat greater detail in FIG. 4 of the drawing. The feed means 14 comprises a substantially rectilinear structure defined by the upper portion of end wall of the flotation apparatus, feed means outer wall 45, feed means side walls 46 and 47, and feed means bottom wall 48. A vertically extending partition 49 divides the feed means 14 into a pulp feed mixing compartment 50 and a pulp feed distribution compartment 51, and a horizontally extending partition 52 provides for a fluidizing water compartment 53 below the pulp feed mixing compartment 50. The fluidizing water compartment 53 is provided with a water inlet opening 54 through which fluidizing water and selected flotation re agents can be introduced into the compartment 53. The horizontal partition 52 is formed with a plurality of fluidizing water orifices 55 through which fluidizing Water or a mixture of Water and flotation reagents can flow into the feed mixing compartment 5th, the vertical partition 49 is formed with a plurality of openings 56 through which conditioned aqueous pulp can flow into the feed distribution compartment 51, and the end wall 25 is formed with a plurality of feed distribution openings 57 through which the conditioned aqueous pulp can be introduced into and uniformly distributed across the upper portion of the aqueous pulp in the flotation compartment 10.

In operation, an aqueous slurry of the mixture of particulate matter to be treated in our flotation apparatus is introduced into the feed mixing compartment 5t} as indicated by the arrows in FIG. 4, and water or a mixture of water and selected flotation reagents are introduced into the fluidizing Water compartment 53 through water inlet opening 54. The fluidizing Water or the mixture of water and flotation reagents flows upwardly through the orifices 55 into the feed mixing compartment 59 where the fluidizing water and reagents are gently but thoroughly mixed with the particulate feed material therein. The conditioned feed material flows through the openings 56 formed in the vertical partition 49 into the feed distribution compartment 52 as indicated by the arrow in FIG 4, and from thence the conditioned pulp flows through the feed distribution openings 57 formed in the side wall 25 into the body of aqueous puip contained in the flotation compartment 19. A semi-submerged pulp distributing weir 58 located in the flotation compartment 1% below the feed distributing openings 57 further promotes uniform distribution of conditioned pulp throughout the body of aqueous pulp in the flotation compartment.

The froth cleaner compartment to of the embodiment of our new flotation apparatus shown in FIGS. 1 and 2 is shown in somewhat greater detail in FIGS. 6 of the drawings. As previously noted, the cleaner compartment 16 is defined by the upper portion of the end wall 24, the lateral extensions of the side walls 22 and 23, the outer wall 28, and the slanted bottom wall 29 of the cleaner compartment. The cleaner compartment it; communicates with the flotation compartment iii by means of a small opening 6i) formed in the side wall 24, and the compartment 16 contains an esssentially quiescent body of an aqueous medium that is substantially free of suspended particulate matter (apart from very fine divided slime-like particles which settle from the aqueous medium very slowly, if at all). The froth or bubble column that forms on the upper surface of the aqueous pulp in the flotation compartment 16 contains floatable particles from the aqueous pulp, and in addition the froth contains a minor quantity of essentially non-floatable particles that accidentally become entrained in the froth. The froth from the flotation compartment 10 flows over the weir-like froth overflow means 15 into the froth cleaner compartment 16 and onto the quiescent body of the aqueous medium therein. As the froth floating on top of the aqueous medium in the froth cleaner compartment 16 moves from the rougher float overflow means 15 to the cleaner float overflow means 17 at the upper edge of the outer wall 28 of the cleaner compartment, the essentially non-floatable particles which are entrained in the froth have an opportunity to drop from the froth into the quiescent aqueous medium therebelow. If desired, the froth in the froth cleaner compartment 16 can be sprayed with water (as, for that matter, can be froth in the flotation compartment 10) to encourage the essentially non-floatable particles to drop therefrom. Ac cordingly, there is provided a water spray means 193 which distributes a stream of water evenly over the froth in the flotation compartment 16 to induce nonflotatable particles to gravitate downwardly. The non-float particles which drop from the froth into the aqueous medium in the cleaner compartment 16 settle onto the bottom wall 29 of the cleaner compartment. There is a slow movement of aqueous medium from the froth cleaner compartment 16 through the small opening 6% formed in the end wall 24 into the flotation compartment 10, and

9 this slow movement carries with it the non-float particles which accumulate at the bottom wall 29 of the froth cleaner compartment, whereby returning these particles to the aqueous pulp in the flotation compartment.

The pulp level control box 19 of the flotation apparatus shown in FIGS. 1 and 2 is of essentially conventional construction. The level control box is provided with a conduit 70 which connects the level control box with the aqueous pulp in the flotation compartment preferably at the lower end of the flotation compartment and advantageously at the pulp underflow discharge means 18 as shown in FIG. 1 of the drawing. The level control box 19 shown in the drawing is a substantially rectilinear structure that is defined by end walls 62 and 63, and side walls 64 and 65. It is divided by a vertical partition 66 into a fluid compartment 67 and an overflow compartment 68, the upper edge of the vertical partition 66 being at the same level as the roughter froth overflow means 15 of the flotation compartment 10. The lower end of the fluid compartment 67 communicates by means of the conduit 6-9 and underflow discharge means 18 with the aqueous pulp in the flotation compartment 10, and the bottom wall 70 of the overflow compartment 68 is provided with overflow discharge means 71. The level control means 19 is intended to prevent disruptive flooding of the flotation compartment 10 when, inadvertently, excess fluid is introduced or surges into the flotation compartment. When such an excess of fluid enters the flotation compartment 10 the liquid level rises in the fluid compartment 67 of the level control box 19 and overflows into the overflow compartment 68 of the box 19, thereby quickly and automatically controlling the liquid level in the flotation compartment 10.

The flotation apparatus shown in FIG. 1 of the drawing is provided with underflow discharge means 18 adapted to withdraw the non-float fraction of particulate matter from the flotation compartment 10 with a minimum of disruption of the desired quiescent condition of the pulp in the flotation compartment. To accomplish this result, the non-float fraction is withdrawn from the flotation compartment 10 at as low a linear velocity as is compatible with satisfactory operation of the apparatus and as the physical limitations of the space available will permit. That is to say, We have found that the relatively small diameter pipes or conduits employed as the pulp underflow discharge means in conventional pneumatic flotation machines require that the underflow be withdrawn from the flotation compartment of lsuch machines at a relatively high velocity, and that the high velocity of the underflow discharge creates currents in the body of aqueous pulp that disrupt the desired quiescent condition of the pulp and adversely affect flota- {tion efficiencies. Moreover, in accordance with this discovery, we have found that, ideally, the underflow frac tion should be withdrawn from the lower portion of the flotation compartment at the same rate of speed or linear velocity that the non-float fraction of the aqueous pulp will descend in a truly quiescent portion of the aqueous pulp, and, therefore, that the cross-sectional area of the pulp discharge opening 73 of the underflow discharge means 18, ideally, should be at least equal to the cross-sectional area of the flotation compartment 10. In practice, the cross-sectional area of the underflow discharge opening 73 is usually somewhat less than the cross-sectional area of the flotation compartment. However, the discharge opening 73 of the discharge, means 18 has a sufficiently large crosssectional area to reduce the linear velocity of underflow material being withdrawn therethrough to a level such that the aqueous pulp in the lower portion of the flotation compartment 10 is essentially undisturbed by the withdrawal of said underflow material.

In the embodiment of our invention shown in FIG. of the drawing the flotation compartment 75 has a cylindrical configuration, the aqueous pulp being introduced into the cylindrical flotation compartment by means of the centrally positioned pulp feed means 76 and pulp distribution means 77 disposed at the upper end of the flotation compartment. The float fraction overflows from the flotation compartment 75 at the froth overflow means 78 which forms the upper edge of the cylindrical flotation compartment, the overflow fraction being collected in the annular overflow launder 79 from which it is withdrawn by the overflow discharge conduit 81 The non-float fraction of the aqueous pulp is withdrawn from the flotation compartment 75 through the annular opening 82 of the low velocity discharge means 83, the cross-sectional area of the annular opening 82 being approximately equal to the cross-sectional area of the cylindrical flotation compartment 75. A cylindrical hydraulic compartment 85 is disposed directly beneath the flotation compartment 75 and is separated therefrom by a constriction plate 86 formed with a plurality of orifices 87 of the type previously described. The hydraulic compartment 85 is provided with a mechanically operated impeller-type air diffuser 89, the air diffuser shown in FIG. 5 being of the rotary, air aspirating type that is employed in Pagergren flotation machines. Water is introduced into the hydraulic compartment 85 through the water inlet conduit 90, and air is drawn into the hydraulic compartment through the air inlet conduit 91 when the air diffuser is in operation. The high speed rotation of the squirrel cage impeller 92 of the air diffuser 89 vigorously agitates the water in the hydraulic compartment and simultaneously draws in air through conduit 91 and disperses this air throughout the water in the compartment 85. Although only one mechanically operated air diffuser 89 is employed in the embodiment of our invention shown in FIG. 5, other embodiments of our invention (for example, the embodiment shown in FIG. 1) might require more than one such air difluser in each hydraulic compartment to insure adequate diffusion of air and uniform dis tribution of aerated water throughout the compartment.

In the embodiment of our invention shown in FIGS. 7, 8, and 9 of the drawing the flotation apparatus is provided with two flotation compartments, the second flotation compartment being disposed with respect to the first so that the underflow fraction withdrawn from the first compartment flows generally horizontally through the second compartment and is discharged therefrom after being subjected to a second flotation operation, The first flotation compartment 95, is provided with a pulp feed mixer and distributor 96, froth overflow discharge means 97, a froth cleaner compartment 98, a low velocity underflow discharge opening 99, and a hydraulic compartment 100. The hydraulic compartment 100 is divided into two hydraulic compartment sections 100a and 1001) by a vertical partition 101. A constriction plate 102 separates the hydraulic compartment from the flotation compartment, the constriction plate being formed with orifices 103 through which aerated water from the hydraulic compartment is introduced into the flotation compartment Water-jet type air diffusers 104 of the type previously lescribed are associated with each hydraulic compartment section.

The second flotation compartment 106 is positioned immediately next to the first flotation compartment and communicates therewith through the low velocity underflow discharge opening 99 formed in the side Wall 107 common to both the first and second flotation compartments. The aqueous pulp feed material for the second flotation compartment 106 comprises the underflow or non-flotation fraction withdrawn from the first flotation compartment 95 through the discharge opening 99, and the opening 99 may therefore be regarded as the pulp feed means for the second flotation compartment. The second flotation compartment 106 is provided with froth overflow discharge means 108, a froth cleaner compart ment 109, and a low velocity discharge opening 110. A

hydraulic compartment 11 advantageously divided into two hydraulic compartment sections 111a and 111!) by a vertical partition is positioned below the second flotation compartment 1136. A constriction plate 113 formed with orifices 114 separates the hydraulic compartment 111 from the flotation compartment 1%. Water-jet type air diffusers 104 are also provided for aerating the water contained in the hydraulic compartment 111. Pulp level control means 116 of the type previously described is disposed adjacent the second flotation compartment 105, the pulp level control means communicating with the flotation compartment 1% by means of the conduit 117 and the underflow discharge opening 110 of this flotation compartment. Moreover, the second flotation compartment 1tl6 may conveniently be provided with a water spray means 194 which distributes an even spray of water over the froth contained in the said compartment to encourage any essentially non-flotatable particles to drop therefrom. The second flotation compartment 1% may also be provided with air diffuser means 195 which introduce aerating air directly to the aqueous pulp contained in the said compartment to more readily induce separations of the pulp and which is of the perforated rubber type described in United States Patent 2,758,714 to Hollingr worth.

In operation, the feed material to be subjected to froth flotation in our two compartment flotation cell is introduced into the pulp feed mixing compartment 118 of the pulp feed mixer and distributor where the feed material is mixed and conditioned with fluidizing Water or with a mixture of water and selected flotation reagents from the fluidizing water compartment 119. The conditioned pulp flows into the pulp distribution compartment 126 and from thence through the pulp feed openings 121 of the pulp feed mixer and distributor 96 into the first flotation compartment 95. Aerated water from the hydraulic compartment 100 enters the lower portion of the flotation compantment 95 through the orifice 103 formed in the constriction plate 162. The minute air bubbles in the aerated water thus introduced into the flotation compartment 95 rise through the aqueous pulp therein to form a froth on the surface of the pulp that contains floated particles of the particulate matter from the aqueous pulp. The froth containing the rougher float fraction is discharged from the flotation compartment 95 over the rougher float overflow means 7 into the froth cleaner compartment 98. Non-float particles inadvertently entrained in the froth have an opportunity to drop therefrom as the forth moves across the cleaner compartment 98 toward the cleaner float overflow means 122, the non-float particles being returned to the aqueous pulp in the flotation compartment 95 through the small opening 123 at the lower end of the cleaner compartment 98 in the manner previously described. The clean froth from the froth cleaner compartment 98 is discharged therefrom over ..the cleaner float overflow means 123. "r

The underflow fraction containing the non-float particles of the aqueous pulp, together with some float particles which escaped flotation, is withdrawn from the first flotation compartment 95 through the low velocity underflow discharge opening 99 and is introduced into the lower portion of the second flotation compartment 106. The aqueous pulp thus introduced into the second flotation compartment 106 is subjected to a second flotation operation therein, a plurality of streams of aerated water being introduced into the second flotation compartment through the orifices 114 formed in the constriction plate 113 for this purpose. Floatable panticles contained in the aqueous pulp in the second flotation compartment are carried by the air bubbles rising in the aqueous pulp to the top of the pulp where a froth containing said floatable particles is formed. The froth from the second flotation compartment 1% is discharged therefrom over the rougher float overflow means 108 into the froth cleaner compartment 169, non-float particles drop from the froth 1.2 in the cleaner compartment 169 and are returned to the flotation compartment 106 as previously described, and a clean froth is discharged from the froth cleaner compartment over the cleaner float overflow means 124. Non floatable particles contained in the aqueous pulp in the second flotation compartment are supported or maintained in suspension by the streams of aerated water introduced into the compartment through the orifices 114, and the fluidized aqueous pulp is transported generally horizontally across the lower portion of the compartment 109 from the inlet opening 9% to the discharge opening 110. The underflow from the second flotation compartment is discharged therefrom through the low velocity discharge opening 119, and then is withdrawn from the flotation apparatus through the underflow discharge conduit 126.

in the embodiment of our invention shown in FIG. 10'

of the drawing the flotation apparatus is provided with four flotation compartments, the four compartments being disposed side by side as described in connection with thepreceeding embodiment so that the underflow fraction withdrawn from the first flotation compartment flows generally horizontally Ithrough the second flotation cornpartment 140, the underflow from the second compartment flows generally horizontally through the third cornpartment 150, and the underflow from the third compartment flows generally horizontally through the fourth flotation compartment 160, the aqueous pulp being subjected to separate flotation operations in each successive flotation compartment. The first flotation compartment 130 is provided with a pulp feed mixer and distributor 131, froth overflow means 132, a froth cleaner compartment 133, cleaner froth overflow means 134, a low velocity underflow opening, a constriction plate 136 formed with orifices 137, a hydraulic compartment 138 and water-jet type air diffusers 139. Similarly, the second flotation compartment 149, the third flotation compartment and the fourth flotation compartment are each respectively provided with froth overflow means 142, 152 and 162;

a froth cleaner compartment 143, 153 and 163; a cleanerfroth overflow means 144, 154 and 164; a low velocity underflow opening 145, 155 and 165; constriction plate 136 formed with orifices 137; a hydraulic compartment 148, 158 and 168; and water-jet type air diflusers 149, 159 and 169. In addition, the side walls 171, 172 and 173 separating the first and second, the second and third, and the third and fourth flotation compartments, respectively, are each provided with adjustable weirs 174, 175 and 176, respectively, which can be adjusted to promote or curtail movement of the froth formed on the surface of the aqueous pulp in one flotation compartment into the adjoining flotation compartment.

In operation, the four compartment flotation apparatus shown in FIG. 10 functions in essentially the same manner as does the two compartment flotation apparatus shown in FIGS. 7, 8 and 9, the aqueous pulp being subjected to a separate flotation operation in each compartment as previously described. The aerated water entering the lower portion of each flotation compartment supports the solid material in the pulp as the pulp moves in a generally horizontal direction across the lower portion of the compart ment toward the underflow discharge opening thereof. The froth that forms on the surface of the pulp or aqueous medium in each flotation compartment is discharged over the froth overflow means of that compartment into the froth cleaner compartment associated therewith, and from thence over the cleaner froth overflow means to a launder or the like where the froth is collected. By appropriate adjustment of the adjustable weirs 174, 175 and 176 bet-ween each flotation compartment, a portion of the froth formed in each flotation compartment can be caused to flow to the next adjoining compartment counter-current to the flow of the main body of the aqueous pulp in the lower portion of the apparatus, with' consequent improvement in mineral separation and recovery,

Certain aqueous pulps (forexample, those which contain certain difficult-to-float materials) may require more aerating air to obtain satisfactory separations than can be conveniently introduced into the flotation compartment through the orifices formed in the constriction plate of our flotation apparatus. In such cases it may be desirable to introduce an additional quantity of aerating air directly into the aqueous pulp in the flotation compartment, and the modification of our apparatus shown in FIG. 11 of the drawing is specifically designed to accomplish this result. The flotation apparatus shown in FIG. 11 comprises a flotation compartment 180, pulp feed mixer and distributor 181, rougher float overflow means182, froth cleaner compartment 183, cleaner float overflow means 184, low velocity discharge means 185, hydraulic compartment 186, and water-jet type air diffusers 187. The flotation compartment 180 additionally is provided with air diffusers 189 adapted to introduce aerating air directly into the aqueous pulp contained in the flotation compartment, the air. diffusers 189 advantageously being of the perforated rubber type described in US. Patent 2,758,714 to Hollingsworth. The use of air diffusers in direct contact with the aqueous pulp contained in the flotation compartment 180 gives rise to the possibility that the minute air bubble control openings of the air diffusers will become clogged with a coating of the fine particulate matter and oily flotation reagents present in the aqueous pulp, and therefore such use is warranted only when the requirement for additional air outweighs the disadvantages resulting therefrom.

FIG. 12 shows the lower portion of a cylindrical flotation apparatus similar to that shown in FIG. of the drawing. The flotation compartment 75 of the apparatus is divided by vertically extending partitions 191 and 192 into a plurality of smaller flotation compartment sections, the lower ends of which terminate an appreciable disstance above the constriction plate that serves as the bottom wall of the flotation compartment. In the modification of our flotation apparatus shown in FIG. 12, aerated water is introduced into the lower portion of the flotation compartment 75 from a single hydraulic compartment disposed therebeneath. In another modification of this flotation apparatus the hydraulic compartment is divided by appropriate vertical partitions into a number of smaller hydraulic compartment sections, each hydraulic compartment section being provided with one or more air diffusers in a manner similar to that shown in FIG. 7 of the drawmg.

The essential features of our invention can be incorporated in flotation apparatus wherein the feed material is introduced into the upper portion of the flotation compartment (for example, as in the apparatus shown in FIG. 1 of the drawing), wherein the feed material is introduced into the lower portion of the flotation compartment (for example, as in the second flotation compartment of the apparatus shown in FIG. 8), or wherein the feed material is introduced into the flotation compartment at any level therebetween. Moreover, the height or depth of the flotation compartment of the apparatus embodying the features of our invention is not critical, the manner of introducing aerated water into the lower portion of the flotation compartment from a separate hydraulic com-' partment therebeneath, the provision for low velocity discharge of the underflow material, and the like being applicable to flotation apparatus of all sizes and shapes. In particular the essential features. of our invention can be incorporated in apparatus adapted to carry out a fractionating flotation operation such as that described in copen'ding application 'Ser. No. 318,393 of Hollingswort-h, now United States Patent No. 3,298,519, patented Jan. 17, 1967'.

Both water-jetitype air diffusers such as those shown in FIG. '1 'andmechanically operated impeller-type air diffusers such as that shown in FIG. 5 insure the forrria:

tion of a uniform dispersion of minute air bubbles throughout the water in the hydraulic compartment of the apparatus. However, to help promote the formation of the desired dispersion of air bubbles throughout the water in the hydraulic compartment, and to help maintain the dispersion of air bubbles after the aerated water is introduced into the flotation compartment of the apparatus, it has been found advantageous to add a surfacta ant to the water being introduced into the hydraulic compartment. The surfactant, as noted, is added to the water in the hydraulic compartment to promote and maintain the dispersion of air in the aqueous medium, and it is not employed for the purpose of modifying the activity of the flotation reagents present in the conditioned aqueous pulp, as has heretofore been proposed by workers skilled in this art. However, the surfactant added to the water in the hydraulic compartment should be compatible with the flotation reagent with which the aqueous pulp is conditioned; for example, a cationic surfactant should not be used with an anionic flotation reagent if there is any likelihood that the two will react and thus nullify the effectiveness of both reagents. Surfactants useful in the practice of our invention include alkyl aryl sulfonates, sulfonated alcohols, alkyl and alkenyl esters of sulfonic acid, polyethylene ether derivatives of fatty acids and of alkyl phenols, esters and ether-esters derived from anhydrides of hexahydric alcohols, long chain quaternary ammonium salts, and the like.

The following specific examples are illustrative but not limitative of the practice of our invention.

Example I A feed material comprising essentially a mixture 01 silica and phosphate rock particles having a particle size of between through 20 mesh and on mesh (Tyler Standard) was conditioned with a cationic flotation reagent to float the silica content thereof, and the conditioned feed was introduced into the upper portion of a cylindrical flotation cell similar to that shown in FIG. 5 of the drawing. The flotation compartment of the cell was 20 inches in diameter and 8 feet in depth. The hydraulic compartment of the cell was separated from the flotation compartment by a constriction plate formed with inch openings on 2 inch centers, and it was provided with a mechanically operated air diffuser from a Fagergren flotation machine. The feed material contained 19.77% by weight bone phosphate of lime (BPL). The overflow fraction contained 0.33% by weight BPL, the balance essentially silica. The underflow or phosphate rougher concentrate contained 47.86% by weight BPL and 39.53% insoluble matter (mainly silica). The feed was conditioned with one half pound of an amine flotation reagent per ton of feed material, and 99.2% of the BPL content of the feed was recovered in the phosphate rougher concentrate. The results are summarized in the following table.

A feed material comprising essentially a mixture of silica and phosphate rock particles in the minus 20 mesh and plus 150 mesh range was introduced into the pulp feed mixer and distributor of a flotation apparatus similar to that shown in FIG. 1 of the drawing where the feed material conditioned with a cationic flotation reagent to float the silica content thereof, and from thence the con- .ditioned feed material was introduced into the upper end of the flotation compartment of said apparatus. The hydraulic compartment of the flotation apparatus was provided with two water-jet air diffusers of the type shown in FIG. 3 which were operated at a water pressure of 35 p.s.i.g. The feed material contained 70.12% by weight BPL, the overflow contained 7.91% by weight BPL, and the phosphate concentrate underflow withdrawn through the low velocity discharge openings of the flotation compartment contained 75.90% by weight BPL and 2.23% by weight insoluble matter. The BPL recovery was 99.3%. These results are summarized in the following table.

TABLE 2 Aanalysis (percent weight):

Feed, BPL 70.12 Concentrate, BPL 75.90 Concentrate, insol. 2.23 v Overflow, BPL 7.91 BPL recovery (percent) 99.3 Reagents (lbs/ton feed):

Aimne -1 0.2

Kerosene 0.4

Example III A feed material comprising essentially silica and phosphate rock particles in the minus 20 mesh to plus 150 mesh range was conditioned with a cationic flotation reagent to float the silica content thereof as in Example II, and the conditioned feed material was introduced into the upper portion of the flotation compartment of the apparatus of Example II. The feed material contained 36.66% by weight BPL, the overflow contained 1.41% by weight BPL, and the underflow phosphate concentrate contained 54.98% by weight BPL.

An additional quantity of substantially the same con ditioned feed material was introduced into the flotation compartment of the apparatus, and a surfactant was added to the water introduced into the hydraulic compartment of the cell at a rate of 0.05 pound of surfactant per ton of feed in order to promote air bubble formation and bubble size stability. The feed material contained 35.03% by weight BPL, the overflow contained 1.30% by weight BPL, and the underflow phosphate concentrate contained 63.74% by weight BPL. The improved results obtained are attributable to the surfactant added to the water in the hydraulic compartment. These results are summarized in the following table:

TABLE 3 Without Surfactant With Surfactant Analysis (Percent by weight) eed, 36. 66 35.03 Concentrate, BPL. 54. 98 63. 74 C centrate,-ins01 29. 16 18. 13 Overflow, BPL 1. 41 1.30 BPL recovery (Percent) 98.7 98. 4 Reagents (lbs. Iton feed):

Amine 0. 75 0. 75 Surfactant 0. 05

Example IV tained 65.36% by weight BPL. These results are sum-- marized in the following table:

18 TABLE 4 Analysis (percent by weight):

Feed, BPL 36.15 Concentrate, BPL .Q- 65.36 Concentrate, insol. 15.02 Overflow, BPL- 2.11 BPL recovery (percent) 97.2 Reagents (lbs/ton feed): Amine 0.93

Example V TABLE 5 BPL, percent by weight Froth from flotation compartment 5.38 Froth from cleaner compartment 3.62

Example VI A feed material comprising essentially silica and phosphate rock particles in the minus 20 mesh plus mesh range was conditioned with an anionic flotation reagent to float the phosphate content thereof, and the conditioned pulp was introduced into the upper portion of the first flotation compartmentfof a two compartment flotation apparatus similar to that shown in FIGS. 7 and 8 of the drawing. A further quantity of the same conditioned pulp was introduced into the first of a series of four conventional mechanical MS sub-aeration flotation machines. The results obtained with the two compartment flotation cell of our invention and with the series of four conventional sub-aeration machines are compared in the following table:

Reagents (lbs/ton iced): rfii oili fatty acid and caustic so a Example VII Mixtures of relatively coarse particles of silica and phosphate rock, for example, particles in the 14 to +35 mesh range, cannot be separated efficiently and eco nomically' by froth flotation in conventional flotation machines, and as aresult, such coarse feed material is' commonly beneficiated on spray belts of the type known in the art. To demonstrate the capability of the flotation apparatus of our invention to beneficiate such coarse material, identical samples of a feed material comprising essentially silica and phosphate rock particles in the -14 to +35 mesh range and containing 38.52% by weight BPL.were conditioned with identical quantities of an anionic flotation reagent, and one sample was then bene-' ficiated on conventional spray belts and the other sample was beneficiated in flotation apparatus similar to that shown in FIGS. 7 and 8 of the drawing. A rougher belt and a cleaner belt were employed in the spray belt circuit, the underflow from the rougher belt being discarded as tails and the underflow from the cleaner belt being recycled as a middling product to the sizing screens of the feed preparation plant. As a result, it was not possible to determine how much, if any, of the BPL content of the middling product was ultimately recovered. If all of the midds were lost, the overall BPL recovery of the spray belts would have been 79.0%. If all of the midds were introducing the conditioned pulp into a flotation compartment containing a relatively quiescent body of saidaqueous pulp,

introducing air and water into a hydraulic compartment disposed directly below the flotation compartment subsequently recovered, the BPL recovery of the belt while simultaneously producing and dispersing a circuit would have been 88.6%. The BPL recovery of multitude of fine bubbles of said air throughout the the flotation apparatus of our invention was 92.6%. The water in the hydraulic compartment, said hydraulic superior results obtained with the two compartment flocompartment being in fluid communication with the tation apparatus of our invention as compared with the lower portion of the flotation compartment through results obtained by the use of spray belts are shown in a plurality of orifices formed in the bottom wall of the following table: said flotation compartment,

TABLE 7 I F d Concentrate Middlings Tailings Percent BPL Recovery ee BPL Percent BPL Insol. Percent BPL Percent BPL Midds Midds Ave. Wt. Wt. Wt. Lost Rec.

38. 52 45. 0 67. 57 15. 77 42. 7 1e. 51 12. a 8.81 79. 0 86. 6 83.8 38.52 52.6 67. so 14. 31 47.4 5.83 92.6

Example Vlll uniformly distributing aerated water from the hydraulic: To demonstrate the improved metallurgy that can be Compartment Into. the l0wer.prtin of flotation obtained when a surfactant is added to the water in the f z g i i the f fortmed m the hydraulic compartment in the practice of our invention, 9? 2 Ion compaf t d identical samples of a feed material comprising essentially i i S a pretssuret O 5;, e silica and phosphate rock particles in the -14 to +15 y mu m fi men h g T We 6 mesh range and containing 35.00% by weight BPL were 2 1c i g t e aqueozls Pu p m t e conditioned with the same quantity of an anionic flota- 5 ffP ment g 2 tion reagent. One sample was then beneficiated in flotation o Tom 6 o a Ion compar f 1n 0 B Y- apparatus similar to that shown in FIGS. 7 and 8 of the drauhc compartment through. the orifices formed drawing without the addition of a surfactant thereto the bottom Wan of the flotatlon compartment while the other sample was beneficiated in the same flotation apparatus with the addition to the water in the first hydraulic compartment of 0.03 pound of a surfactant per ton of feed material being introduced into the first flotation compartment. The improved results that were obtained as a result of the addition of a surfactant to the water in the hydraulic compartment are summarized in the following table:

TABLE 8 Without With Surfactant Surfactant Analysis (Percent by weight):

Feed, BPL 35. 00 35. 00 Concentrate, BPL 74. 51 71. 32 Concentrate, insol 6. 77 11. 20 Underfiow, BPL 15.19 2. 42 BPL Recovery (percent) 71.2 96. 6 Reagent (lbsJton feed): Surf act ant) 0. 03

In all tests the pressure in the hydraulic compartment was not permitted to drop below 1 p.s.i.g. in order to prevent pulp from entering the hydraulic compartment, and we usually operated in the range of 2 to 4 p.s.i.g.

From the foregoing description of our new process and apparatus for effecting the separation of particulate matter by froth flotation, it will be seen that we have made an important contribution to the art to which our invention relates.

We claim:

1. Process for concentration of minerals by froth flotation of an aqueous pulp containing a mixture of mineral particles and gangue particles which comprises withdrawing an overflow float fraction containing floated particles of pulp from the top of the body of aqueous pulp in the flotation compartment, and

withdrawing an underflow fraction containing nonfloated particles of the pulp from the lower portion of the flotation compartment. 2. The process according to claim 1 in which the float fraction from the flotation compartment is introduced onto the top of a relatively quiescent non-aerated body of an aqueous medium contained in a float cleaner compartment immediately adjacent the top of the flotation'comp-artment whereby non-float particles entrained in the float fraction drop from said float fraction into said aqueous medium, the cleaned float fraction thereupon being withdrawn from the top of the aqueous medium in the cleaner compartment and the float fraction on the aqueous medium in the float cleaner compartment is sprayed with water to promote dislodgement of non-float particles entrained in the float fraction.

3. The process according to claim 1 in which a surfactant is added to the aerated water in the hydraulic compartment andthe non-float fraction is withdrawn from the; flotation compartment through a relatively large underflow discharge opening so that the linear velocity of the aqueous pulp being withdrawn tzherethrough approaches the velocity at which the non-float fraction sinks in a substantially quiescent body of the aqueous pulp in said floatation compartment.

4. The process according to claim 1 in which the nonflotation compartment is introduced into the lowerportion of a second flotation compartment disposed immediately adjacent the first flotation compartment, said second flotation compartment containing a body of the v aqueous pulp substantially depleted in floatable particles;

' reagent adapted to promote flotation of one of the f types of particles present in the aqueous pulp when the pulp is aerated,

in'which a body of aerated water is established in a hydraulic compartment disposed directly below the second flotation compartment by introducing air and water into said hydraulic compartment while simultaneously dispersing a multitude of fine bubbles of said air throughout the water in the hydraulic compartment, said hydraulic compartment being in fluid communication with the lower portion of the second flotation compartment through a plurality of orifices formed in bottom wall of said flotation compartment; in which aerated water from the hydraulic compartment is introduced into the lower portion of the second flotation compartment through the orifices formed in the bottom wall of said flotation compartment; in which the static pressure of the aerated water in the hydraulic compartment is maintained sufliciently above the staticvpressure of the aqueous pulp in the lower portion of the second flotation compartment to prevent the flow of pulp from said flotation compartment into the hydraulic compartment through the orifices formed in the bottom wall of the flotation compartment; in which an overflow or float fraction containing floated particles of the pulp is withdrawn from the top of the body of aqueous pulp in the second flotation compartment; and in which an underflow or non-float fraction containing nonfloated particles of the pulp is withdrawn from the lower portion of the second flotation compartment.

5. The process according to claim 4 in which the float fraction on the aqueous pulp in the second flotation compartment is sprayed with water to promote dislodgement of non-float particles entrained in the float fraction.

6. The process according to claim 4 in which the float fraction from the second flotation compartment is introduced onto the top of a relatively quiescent non-aerated body of an aqueous medium contained in a float cleaner compartment whereby non-float particles entrained in the float fraction drop from said float fraction into said aqueous medium, the cleaned float fraction thereupon being withdrawn from the top of the aqueous medium in the cleaner compartment, and the float fraction on the aqueous medium in the float cleaner compartment is sprayed with Water to promote dislodgement of non-float particles entrained in the float fraction.

7. The process according to claim 4 in which a surfactant is added to the aerated water in the hydraulic compartment below the second flotation compartment and the non-float fraction is withdrawn from the second flotation compartment through a relatively large opening so that the linear velocity of the aqueous pulp being withdrawn thereat is relatively low.

8. The process according to claim 4 in which at least a portion of the float fraction on the aqueous pulp in the second flotation compartment is recycled onto the aqueous pulp in the first flotation compartment and the non-float fraction withdrawn from the lower portion of the second flotation compartment is subjected to at least one additional froth flotation operation substantially as carried out in the second flotation compartment.

9. Apparatus for effecting concentration of minerals by froth flotation of an aqueous pulp containing a mixture of mineral particles and gangue particles which comprises a flotation compartment adapted to contain a relatively quiescent body of said aqueous pulp,

pulp feed means adapted to introduce said aqueous pulp into the flotation compartment,

.froth overflow means disposed adjacent the upper end of the flotation compartment adapted to discharge therefrom a float fraction containing floated particles of said aqueous pulp,

underflow discharge means positioned adjacent the lower end of the flotation compartment adapted to discharge therefrom a non-float fraction containing unfloated particles of said aqueous pulp,

a hydraulic compartment disposed beneath the flotation compartment, said hydraulic compartment being adapted to contain a 'body of aerated water maintained at an appreciably higher static pressure than that of the aqueous pulp in the lower portion of the flotation compartment,

a constriction plate separating the flotation compartment from the hydraulic compartment disposed therebeneath, said constriction plate being formed with a plurality of geometrically spaced orifices for uniformly distributing aerated water from the hydraulic compartment to the flotation compartment, each orifice adapted to permit a stream of aerated water to flow from said hydraulic compartment into the lower portion of said flotation compartment,

means for introducing water into said hydraulic compartment,

means for introducing air into said hydraulic compartment, and

means for uniformly forming and dispersing a multitude of minute air bubbles throughout the water in the hydraulic compartment.

10. The apparatus according to claim 9 in which the hydraulic compartment is provided with at least one air aspirating water-jet air diffuser adapted simultaneously to introduce water into the hydraulic compartment, to introduce air into and disperse said air in the form of minute air bubbles throughout said water, and to distribute the resulting aerating water uniformly throughout the hydraulic compartment.

11. The apparatus according to claim 9 in which the" hydraulic compartment is provided with an air aspirating, rotating impeller air diffuser adapted to simultaneously introduce air into the hydraulic compartment, to disperse said air in the form of minute air bubbles throughout the water in the hydraulic compartment, and to distribute the resulting aerated water uniformly throughout the hydraulic compartment.

12. The apparatus according to claim 9' in which the cross-sectional area of the discharge opening of the underflow discharge means is sufficiently large to permit the underflow material to be withdrawn from the flotation compartment at a linear velocity approaching the velocity at which the non-float fraction will sink in a substantially quiescent body of aqueous pulp in said flotation compartment.

13. The apparatus according to claim 9 in which a froth cleaner compartment adapted to contain a non-aerated, essentially quiescent aqueous medium is provided adjacent the froth overflow means of the flotation compartment, the lower portion of said froth cleaner compartment communicating with the flotation compartment through a small orifice formed in the side wall thereof, the upper edge of the outer wall of said froth cleaner compartment being provided with froth overflow means adapted to discharge cleaner froth therefrom and the flotation compartment is divided by at least one vertical partition into a plurality of smaller flotation compartment sections.

14. The apparatus according to claim 9 in which the pulp feed means comprises a pulp conditioning compartment, a fluidizing water compartment disposed below said pulp conditioning compartment and in fluid communica tion therewith through orifices formed in the bottom wall of the pulp conditioning compartment, and a pulp distribution compartment disposed adjacent said pulp c-onditioning compartment and in fluid communication therewith through orifices formed in one of the side Walls of the pulp conditioning compartment, said pulp distribution compartment being provided with pulp distribution means adapted to introduce conditioned pulp into the flotation compartment of the apparatus; and water spray means are provided for spraying the float fraction on the aqueous medium in the flotation compartment.

15. The apparatus according to claim 9 in which air diffuser means are disposed in the flotation compartment for introducing additional aerating air directly into the aqueous pulp contained therein.

16. The apparatus according to claim 9 in which a second flotation compartment is disposed with respect to the aforesaid first flotation compartment so that the underflow material withdrawn from the first flotation compartment through the underflow discharge means thereof is introduced into the lower portion of the second flotation compartment where said underflow material is subjected to a second flotation operation, said second flotation compartment being provided with froth overflow means dis posed adjacent the upper end of the second flotation compartment adapted to discharge therefrom a float fraction containing floated particles of said aqueous pulp, final underflow discharge means positioned adjacent the lower end of the second flotation compartment adapted to discharge therefrom a non-float fraction containing unfloated particles of said aqueous pulp, a hydraulic compartment, disposed beneath the second flotation compartment, said hydraulic compartment being adapted to contain a body of aerated water maintained at an appreciably higher static pressure than that of the aqueous pulp in the lower portion of the second flotation compartment, a constriction plate separating the second flotation compartment from the hydraulic compartment disposed therebeneath, said constriction plate being formed with a plurality of geometrically spaced orifices each adapted to permit a stream of aerated water to flow from said hydraulic compartment into the lower portion of said second flotation compartment, means for introducing water into said hydraulic compartment, means for introducing air into said hydraulic compartment, and means for uniformly dispersing a multitude of minute air bubbles throughout the water in the hydraulic compartment.

17. The apparatus according to claim 16 in which each hydraulic compartment is provided with at least one air aspirating water-jet air diffuser adapted simultaneously to introduce water into the hydraulic compartment, to introduce air into and disperse said air in the form of minute air bubbles throughout said water, and to distrib ute the resulting aerated water uniformly throughout the hydraulic compartment.

18. The apparatus according to claim 16 in which each hydraulic compartment is provided with an air aspirating rotating impeller air diffuser adapted to simultaneously introduce air into the hydraulic compartment, to disperse said air in the form of minute air bubbles throughout the water in the hydraulic compartment, and to distribute the resulting aerated water uniformly throughout the hydraulice compartment.

19. The apparatus according to claim 16 in which the cross-sectional area of the discharge opening of the final underflow discharge means is sufflcientl-y large to permit the underflow material to be withdrawn from the second flotation compartment at a linear velocity approaching the velocity at which the non-float fraction will sink in a substantially quiescent body of aqueous pulp in said flotation compartment and the second flotation compartment is divided by at least one vertical partition into a plurality of smaller flotation compartment sections.

20. The apparatus according to claim 16 in which a froth cleaner compartment adapted to contain a non aerated, essentially quiescent aqueous medium is provided adjacent the froth overflow means of the second flotation compartment, the lower portion of said froth cleaner compartment communicating with the second flotation compartment through a small orifice formed in the side wall thereof, the outer wall of said froth cleaner compartment being provided with froth overflow means adapted to discharge cleaner froth therefrom and in which water spray means are provided for spraying the float fraction on the aqueous medium in the second float compartment.

21. The apparatus according to claim 16 in which air diffuser means are disposed in the second flotation compartment for introducing additional aerating air directly into the aqueous pulp contained therein.

22. The apparatus according to claim 16 in which an adjustable froth overflow Weir is disposed between the first and the second flotation compartments to permit recycling at least a portion of the float fraction from the second to the first flotation compartment.

23. The apparatus according to claim 16 in which at least one additional flotation compartment structurally equivalent to the second flotation compartment is disposed with respect to said second flotation compartment so that the underflow material withdrawn from the second flotation compartment through the underflow discharge means thereof is introduced successively into the lower portion of each of said additional flotation compartments where said underflow material is subjected to at least one additional froth flotation operation.

References Cited UNITED STATES PATENTS 873,586 12/1907 Norris 209170 1,167,335 1/1916 Norris 209170 1,380,650 6/1921 Hebbard 209170 1,471,332 10/1923 Greenawalt 209168 1,518,010 12/1924 Simpson 209-170 1,597,368 8/1926 Meyer 209170 1,952,727 3/1934 Ralston 209170 2,028,179 1/1936 Akins 209170 2,433,592 12/1947 Booth 209168 2,673,724 3/1954 Potts 261-87 2,753,045 7/1956 Hollingsworth 21022l X 2,758,714 8/1956 Hollingsworth 209168 2,783,884 3/1957 Schaub 209- 2,873,600 2/1959 Demaret 261-87 X 3,298,519 1/1967 Hollingsworth 209l66 FOREIGN PATENTS 1,255,877 1/1961 France.

FRANK W. LUTTER, Primary Examiner. HARRY B. THORNTON, TIM R. MILES, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,371 ,779 March 5 1968 Clinton A. Hollingsworth et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 54, "uhen" should read when Column 2, line 24, "areate" should read aerate Column 4, line 71, "partions" should read partitions Column 7, line 22, ""sipe" should read size line 25, "construction"should read constriction Column 8, line'43', "fine" should read finely line 63, "be" secondtccurrence, should read the Column 10, line 69, "non-flotation" should read non-float Column 14,

line 73, before "conditioned" insert was Column 15,

line 21, "Aimne" should read Amine Column 17, line 25, "+l5"'s'hould read +35 Column 18, line 59, after "non'-" insert float fraction withdrawn from the lower portion of said Column 21, lines 37 and 38, "hydraulice" should read''hydraulic Signed and sealed this 29th day of July 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

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