US2577802A

US2577802A - Froth flotation apparatus

Info

Publication number: US2577802A
Application number: US44118A
Authority: US
Inventors: Pearson M Payne
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-08-13
Filing date: 1948-08-13
Publication date: 1951-12-11
Anticipated expiration: 1968-12-11

Description

Dec. 11, 1951 Filed Aug. 13, 1948 PAYNE 2,577,802

FROTH FLOTATION APPARATUS 2 SHEETSSHEET l Fig. 1

INI/E/VTUP PEARSON M B4Y/Vf ATTORNEY Dec. 11, 1951 PAYNE 2,577,802

FROTH FLOTATION APPARATUS Filed Aug. 15, 1948 2 SHEETS-SHEET 2 INVENTOR V PEARSON M. PAYNE ATTORNEY Patented Dec. 11, 1951 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to the processes and techniques of froth flotation, and more particularly to such processes and techniques applied to the selective separation of comminuted, intermixed materials, and has as an object to provide a novel and improved method for the practical development and effective application of known flotative principles.

A further object of the invention is to provide novel and improved typical apparatus susceptible of embodiment in a variety of specific forms for the efficient practice of froth flotation methods.

A further object of the invention is to provide an improved type of impeller efiiciently operable for the froth flotative aeration of liquid pulps.

A further object of the invention is to provide an improved froth flotation method marked by effective pulp aeration consequent directly and H solely upon impeller actuation.

A further object of the invention is to provide improved froth flotation methods and means applicable with enhanced efficiency to separations accomplished through either intermittent-flow, cell type or continuous-flow, trough type pulp receivers.

A further object of the invention is to provide improved froth flotation methods and means susceptible of ready adaptation, with or without process interruption, to efficiently meet the operative requirements characteristic of a given flotative separation.

A further object of the invention is to provide improved froth flotation methods and means characterized by low initial, operating, and maintenance costs, simplicity and flexibility of application to eflicient resolution of particular separatory problems, high adaptability, and maximum effectiveness in the practical adaptation of known pertinent principles to culmination in desired end results.

With the foregoing and other objects in view,

Figure 1 is a side elevation, partly in vertical section, of one simple embodiment of the principles of the invention as applied to and for cooperation with a conventional froth flotation cell. Figure 2 is a fragmentary, detail section verti cally through a modification adaptable to use -"-generation and enhance the persistence of the bubbles to the ultimate development of a relatively deep froth bed built up above and removable from the pulp body, and the same, or other, reagents exercise their selective affinity for pulp solids to entrain such solids into the froth bed whence they may be recovered as an isolated fraction of the pulp body. Conventional methods and apparatus for the practical application of froth flotation principles utilize impeller-type agitators of excessive mass requiring high power input for their actuation, are characterized by complications incident to adequate air supply to and through such agitators, and are exceedingly difficult, ifnot Wholly impractical, or adaptation to successful separations from a continuous ciples in a manner and through means obviating the shortcomings and disadvantages of the hithquacy of a continuing supply of small-size buberto-known techniques.

Quite obviously, the effectiveness of separation by means of froth flotation is to a large degree proportional to the pulp agitation and the adebles throughout the full depth of the pulp body, and it is apparent that efliciency of the separatory operation is served when the requisite agitation may be had through an instrumentality of "'small mass and low operating resistance and at the same time adequate aeration of the pulp body results directly from the actuation of such agitating instrumentality, and from such considerations derive the novel features and operating relationships of the instant invention.

Replacing the large-mass conventional impellers disposed for agitating effect in the lower zones of the pulp body and designed to expel axially-indrawn, or otherwise supplied, air to 3 and only within their zones of agitation, the method of the invention is given effect by means of a whip-type impeller whereof the agitating elements cut the surface of the pulp body in a manner to positively entrain air from above and through said surface to effect bubble generation through the entire pulp body depth as a direct and immediate consequence of the pulp-agitating impeller actuation. Various structural arrangements and combinations, certain of which are illustrated, supply the operative characteristics above set forth and adapt the invention to particular environments and applications. In Figure l, a conventional flotation cell iii of generally rectangular type, which may be one of an intercommunicating battery of like units, is

shown as provided with the usual lowered Wall margin forming a lip I6 at or slightly above the level of the pulp body top surface whereover froth from the bed developed on and above the pulp body may flow or be deflected with its entrapped material to recovery of the latter apart from the pulp wherefrom it has been separated. Any suitable fixed support, such as a beam i'l bridging the'top of the cell, rigidly or adjustably mounts a journal bearing l8 in spaced relation above the cell with its bore axis directed preferably centrally and perpendicular to the top plane of the cell charge, and a shaft 19 is rotatably carried by the bearing is in suitable driven relation with a source of power, such as an electric motor 20 either adjacent or remote from said shaft and its bearing. The shaft i2 is held against reciprocation axially of the bearing it and terminates near the top plane of the normal cell charge where it fixedly mounts a radially-extending, annular flange, or head, 2% from which a plurality of like whip elements 22 fixedly project downwardly of the cell if: in a uniform spacing angularly about the flange 2i and a uniform downward divergence away from the axis of shaft l9 rotation as a conical assembly coaxial with said shaft and characterized by an open base adjacent the floor of the cell E5. The whips 22 are preferably straight, rod-like elements, circular in section, of any suitable material having the requisite properties of resilient stiffness and resistance to abrasion, and, as represented in Figure 8, said whips may be solid cylinders, or, alternatively, they may be tubular elements open at each end, as indicated in Figure 7. Assembled and mounted as shown and described, the whips Z2 rotate with the shaft I9 as the latter is power-actuated to successively open and follow a conical orbit through the cell charge, the lower, free ends of said whips, by virtue of the whip divergence from the axis of rotation, travelling at a linear speed greater than that of their upper ends. Rotation of the whip assembly within the cell charge is productive of agitation and consequent charge turbulence which increases as the speed of assembly rotation is increased up to a certain maximum, dependent to some extent upon the nature and density of the cell charge, beyond which increased speed of assembly rotation may be marked by a decrease in charge agitation, it being hence feasible to regulate the degree of charge agitation through control of the shaft I9 speed of rotation. At even moderate speeds of 7 whip assembly rotation, a vortex is formed in the cases where said whip upper ends were submerged in a quiescent charge, so that the forces generated by rotation of the whip assembly through the cell charge may act to entrain air from above the charge level rearwardly of and longitudinally along each whip 22 to dissemination through the charge as an infinity of smallsize bubbles in a continuing process of generation along each whip length to and in jetted relation from the whip free ends. Manifestly, rapid transit of each whip 22 through the cell charge is productive of eddy currents and a region of reduced pressure in immediate trailing relation therewith, through which region air at atmospheric pressure is impelled to enter and become subject to the eddy currents, while the centrifugal forces of assembly rotation as modified by the whip inclination relative to the axis of rotation tend to entrain the air to the whip free ends and at the same time break up and disseminate the air flow for intense generation of desired small-size bubbles. Whatever may be a correct analysis of the forces, and the bubblegenerating coaction thereof, incident to whip assembly rotation within the cell charge, it is an observable phenomenon that such bubble generation does occur with remarkable volume and facility at low rotative speeds and that the bubble volume and concentration increase as the speed of assembl rotation is increased, up to a critical point dependent upon nature and density of the cell charge beyond which the bubble propagation declines as speed of assembly rotation increases. riving from whip assembly rotation may be regulated and controlled within desired limits by means of baffles and deflectors fixed: within the cell in a usual manner, and the development of undesired vortex effect interiorly of the whip assembly, with the possibility of a consequent dead spot, may be obviated by the provision of a conical baffle 23, either ribbed or unribbed, upstanding fixedly from the floor of the cell I5 coaxially within and surface-spaced from the orbit of said assembly. When tubular elements 22 are employed, rotation of the so-equipped whip assembly induces an air flow through each such element with a consequent supplementing of the bubble-forming jet action at the element free ends.

The vortex-forming tendency of whip assem-- bly rotation in the cell l5 induces a flow of froth inwardly about and towfard the flange 2| to possible resubmergence thereof within the pulp body, thus entailing a possible loss of efliciency through the necessity of reworking once levitated material, but an open-ended, annular collar 24 of suitable diameter and axial length may be fixedly suspended in any convenient manner concentrically about said flange to intersect the pulp charge level and extend both above and below the same as a bafile limiting the spread of-the vortex effect in the pulp surface and damining. the froth away from vortex influence-.-

Figure 3 illustrates a slight modification of the whip assembly above described, wherein the otherwise free, lower ends of the elements 22 are fixed in and serve to support an annulus 25 rotatable with and as a part of the assembly, while in Figure 4 is shownan alternative construction 0 wherein the shaft 19 is extended to the base of Agitation of the cell charge de-' mizing the bending stresses to which the elements 22 are subject, and particularly adapting the whip assembly for use in certain heavy pulps. The modification according to Figure 5 utilizes the extended shaft l9 and plate 26 of Figure 4, but dispenses with the flange 2|, thus leaving the upper ends of the whips 22 free for reaction to the forces generated by assembly revolution, while in Figure 6 the extended shaft [9 of Figure 4 is furnished with a radially-armed spider 2'! through the arm ends whereof the elements 22 engage at their midportions in any desired parallel or inclined relation with the axis of said shaft. Since changes, variations, and modifications in the specific form, construction, and arrangement of the elements pertinent to practice of the improved method may be had without departing from the spirit of my invention,-I wish to be understood as being limited solely by the scope of the appended claims, rather than by any details of the illustrative showing and foregoing description.

I claim as my invention:

1. A froth flotation apparatus comprising a pulp container open to atmospheric air at its top and having an outlet for froth, a shaft rotatably mounted vertically, impellers about said shaft spaced from each other circumferentially thereof and extending downwardly and bein of a length adapting the impellers to be partially submerged in pulp with their upper portions projecting from the pulp, means for rotating said shaft and causing the impellers to move in a circular path and thereby cause air under atmospheric pressure to move downwardly through the pulp along the impellers and then outwardly from the impellers and upwardly through the pulp, and an annular shield surrounding portions of the shaft and the impellers above and below the surface of the pulp and constituting a barrier serving to prevent froth upon the surface of the pulp from being drawn downwardly through a vortex formed during operation of the apparatus.

2. A froth flotation apparatus comprising a pulp container open at its top and having an outlet for pulp at one side, a shaft rotatably mounted vertically, impellers mounted about said shaft in circumferentially spaced relation to each other and consisting of downwardly diverging rods straight throughout their length and being of a length adapting the impellers to be partially submerged in pulp with their upper portions projecting from the surface of the pulp; means for rotating said shaft and causing the impellers to move in a circular path and thereby causing air under atmospheric pressure to follow paths downwardly through the pulp along the rods and then move outwardly and upwardly through the pulp, and an annular shield disposed about portions of the shaft and the impeller rods above and below the surface of the pulp and serving to prevent froth upon the surface of the pulp from being drawn downwardly through a vortex formed during operation of the apparatus.

3. A froth flotation apparatus comprising a pulp container open at its top and having an outlet for froth at one side, a shaft rotatably mounted vertically, impeller rods mounted about said rod in spaced relation to each other circumferentially thereof, said rods being straight and extending downwardly in diverging relation to each other and of a length adapting them to be partially submerged in pulp with their upper portions projecting upwardly out of the pulp, means for rotating said shaft and thereby moving said impeller rods in a circular path and causing air under atmospheric pressure to move downwardly through the pulp along the rods and then move outwardly from the rods and upwardly through the pulp and form froth upon the surface of the pulp, an upwardly tapered conical baffle upon the bottom of said container disposed vertically in axial alignment with said shaft and surrounded by said impeller rods and serving to eliminate a dead spot in the pulp, and an annular shield surrounding portions of the shaft and the rods below and above the surface of the pulp and serving to prevent froth from being drawn downwardly through a vortex formed during operation of the apparatus.

. PEARSON M. PAYNE.

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

UNITED STATES PATENTS Number Name Date 278,985 Luck June 5, 1883 575,499 Andersen Jan. 19, 1897 835,960 Leaver Nov. 13, 1905 901,808 Hamilton Oct. 20, 1908 1,394,306 Hynes Oct. 18, 1921 1,736,073 Fagergren Nov. 19, 1929 2,114,275 Murphy et a1 Apr. 12, 1938 2,385,679 Zacker Sept. 19, 1944