US3023949A - Hydrodynamic ore concentrator - Google Patents

Description

March 6, 1962 E. BANKERD 3,023,949

HYDRODYNAMIC ORE CONCENTRATOR Filed Sept. 3, 1958 2 Sheets-Sheet 1 54 F X Gal. 5

March 6, 1962 HYDRODYNAMIC ORE CONCENTRATOR Filed Sept. 3, 1958 L. E. BANKERD 2 Sheets-Sheet 2 FIG. 4-.

IN V EN TOR.

L/lVCOL/V E BIG/M8590 tats The present invention relates to the art of concentrating metallic ores and particularly to a novel apparatus especially adapted to concentrate crushed metallic ores.

The majority of metallic ores are found in nature in association with high percentages of useless material such as quartz rock. To economically utilize the ore, it is necessary to separate the useful material from the useless before smelting by a process known as concentrating.

A process for concentrating known as forth flotation well known in the art, is used for separating the metallic compound from finely ground rock particles. The flotation process takes advantage of the fact that certain liquids will wet certain substances but not others. These liquids, or flotation reagents, may be mixed with a slurry of finely ground ore and water and upon agitation in the presence of air, a plurality of very fine bubbles coated by the oily flotation reagents, are formed. The fine particles of the metallic compound having been wetted by the flotation reagent, are drawn into the oily film surrounding the minute air bubbles and adhere thereto. The buoyancy of the air bubbles causes the admixture of flotation reagent, air and metallic compound to rise to the surface of the fluid to form a froth which is then separated with an excess of water to provide a mixture of the relatively pure metallic compound and the readily volatile flotation reagent and water. The gangue and other .impurities, including the excess water, are discharged separate from the froth.

In the process of grinding the ore a number of particles too large to be floated by the minute bubbles are formed. These larger particles remain in the main body of the mixture, and generally remain near the bottom of the container utilized. They are thus discharged with the aqueous suspension of gangue.

Generally, the larger and heavier particles may be assumed to contain the same percentage of metallic compound as the original ore. It is, therefore, desirable for reasons of economy that these particles be returned to the grinder for regrinding to release the occluded metallic compound to reduce the loss of useable compound to a minimum.

In the conventional froth flotation process now in use there are no means provided to accurately divide the gangue and the froth. Conventionally, a certain amount of froth and flotation reagent is carried along with the gangue and lost. Since the flotation reagent is expensive, it would be desirable, if possible, to retain as large a percentage of it as possible so that it may be recycled. In addition, because of the turbulence in the flotation cell or container, at certain amount of gangue is sep arated with the froth. The presence of the gangue increases the cost of subsequent smelting and accordingly, is undesirable.

It is an object of the present invention to provide an ore concentrator which will substantially separate the froth, the metal bearing sand and the gangue from one another in a rapid and economically feasible manner.

It is a further object of this invention to provide an ore concentrator by means of which the maximum number of metallic particles are Wetted by the flotation reagent, permitting maximum possible metallic compound recovery.

It is a further object of this invention to provide an ore concentrator especially adapted to permit the formation of a water surface of predetermined characteristics permitting ore bearing froth to be skimmed from the surface thereof readily and conveniently.

It is a further object of this invention to provide a novel means for separating heavier particles of metal bearing sand from useless gangue.

Other objects and advantages will be apparent to those skilled in the art, it is believed, from the following detailed description of the method of concentrating metallic ores and apparatus therefor when taken in connection with the accompanying drawings in which:

FIG. 1 is a horizontal side view of the ore concentrator partially broken away and partially sectionalized.

FIG. 2 is a sectional view taken substantially along the line 2--2 of FIG. 1.

FIG. 3 is a partial sectional View taken substantially along the line 33 of FIG. 1.

FIG. 4 is a graph illustrative of the shape of liquid surfaces formed as a result of the forces of rotation caused by the action of the ore concentrator.

FIG. 5 is an enlarged partial sectional View of the valve means utilized in controlling discharge of the gangue and sand.

Referring now to the drawings:

An ore concentrator in accordance with the present invention is indicated generally at 10. The device, which is rotatably mounted in a frame 12, includes a vessel 14, a baflle assembly indicated generally at 16, and a centrally positioned operation control member indicated generally at 18.

The vessel 14 is provided with an axially extending shaft 20 which is journalled in a bearing 22 carried by the base of the frame 12. The vessel 14 is rotated by a constant speed motor (not shown) which drives the driv ing pinion 24. The driving pinion 24 meshes with a ring gear 26 encircling a lower part of the vessel 14. By this construction the vessel 14 is free to rotate about its central major axis at a speed determined by the constant speed motor. The vessel 14 is generally parabolic in cross section and, as will be more fully shown later, the precise form of the paraboloid is a function of the angular speed of rotation to be imposed upon the vessel in operation. As used throughout this specification the words parabolic in cross section as applied to the Vessel l4 and as is clearly shown in the drawings shall mean that the axial or vertical cross section as determined by a plane intersecting the central vertical axis of the vessel would define a curve which would be generally parabolic. The axial or vertical cross section is to be distinguished from the horizontal cross section, the latter of which would be circular.

The operation control member 18 includes a slurry feed pipe 28, an air feed pipe 3%, a mixing cylinder 32, and a hollow mixing shaft 34. The mixing cylinder 32 is positioned vertically with respect to the vessel 14- and has a central axis which coincides with the central axis of the vessel 14. One end 36 of the mixing cylinder is rotatably mounted in a hearing 38 carried by the top portion of the frame 12;. The other end 46) is provided with a bearing 42 within which is rotatably mounted the mixing shaft 34. In addition, the end 40 is provided with a plurality of bypass channels 44 which communicate between the chamber 46 formed between the inner walls of the mixing cylinder 32 and the exterior surface of the mixing shaft 34 and the lower portion of the vessel 14. The end 4t]! is also provided with a receiving chamber 48 which communicates directly with the bottom of the vessel 14.

The bottom of the vessel 14 is provided with a generally conical protrusion 59 which is axially aligned with the mixing cylinder 32. By this construction fluid flowing from the mixing cylinder 32 into the vessel 14 is urged to follow the flow path represented by the arrows 51.

The slurry feed pipe 28 is provided with a gland 52 encircling the top of the mixing cylinder 32 permitting thereby relative motion between the feed pipe 28 and the mixing cylinder 32. The mixing shaft 34 protrudes above the feed pipe 28 and is journalled in a bearing 54 housed therein. The top of the mixing shaft 34 is connected to the air feed pipe 36, relative motion between the mixing shaft and the air feed pipe being permitted by a gland 56.

The mixing shaft 34 is hollow throughout its length providing, in cooperation with the air feed pipe 30, an air channel 58. Between the feed pipe 28 and the feed pipe 30 is a mixing shaft drive pulley 60 which is powered by a suitable source (not shown) and by means of which the mixing shaft 34 may be rotated with respect to the mixing cylinder 32. The air feed pipe 39 is provided with an air control valve 62 which permits accurate control of the volume of air introduced into the air channel 58. The mixing shaft 34 is provided with a plurality of openings 64 and a plurality of mixing blades 66. By this construction, when slurry is fed through the feed pipe 28 and air through the feed pipe 30, the air and slurry are mixed within the mixing chamber 32 and thoroughly agitated by the mixing blades 66.

As will be more fully explained hereinafter, the mixture of air and slurry introduced into the vessel 14 may be considered as a separable mixture of metal bearing froth, water, gangue and unfioated metallic particles, or sand. Means are provided to individually separate the froth, sand and gangue into separate components.

As will be shown later, the froth migrates to the surface of the slurry. Removal of the froth is accomplished by a plurality of skimmer assemblies as at 68. Each skimmer assembly includes a skimmer 70 mounted on a skimmer bearing 72 which is slidably mounted on the mixing cylinder 32. The skimmer 70 is provided with a skimmer blade 74 which is formed so as to parallel the surface of the water in the vessel 14. The skimmer blade 74 is provided with a froth deflecting chute 76 formed integrally therewith, said chute communicating with a froth discharge conduit 78. The conduit 78 terminates in a froth launder 80 encircling the vessel 14 into which the froth carried by the conduit 78 is discharged. Suitable means are provided to remove the froth from the launder 80.

In order to accurately adjust the skimmer blades 74 with respect to the water surface indicated at 82, the skimmer assemblies are each provided with elevator control means 84. Encircling the upper part of the mixing cylinder 32 are a plurality of elevator gears 86. An elevator bracket 88 threadedly engages the elevator gears 86 and I the bracket 88 is restrained from turning relative to the mixing cylinder 32 by elevator bracket retaining slide 90 which engages a pin 92 fixed to the cylinder 32. Depending from each of the elevator brackets 88 are three skimmer elevator rods 94, each elevator rod being connected to an individual skimmer bearing. Each of the elevator gears 86 is provided with an elevator motor 96 having a worm gear 98 engaging the gear 86. Each of the motors 96 may be individually controlled by suitable electric switches indicated at 100. The elevator gears 86 which are free to turn on the cylinder 32 raise or lower the individual elevator brackets 88 which in turn raise or lower the individual skimmer assemblies 68.

The skimmer 70 is free to rotate in the: bearings 72 and in operation are rotated in a direction opposite the direction of rotation of the Vessel 14. This rotation is accomplished by a turning skimmer motor 102 which drives a turning shaft 104. The turning shaft 10 is provided with a plurality of gears 106 which engage a geared portion 108 of the skimmers 70. By this construction each of the skimmers may be rotated with respect to the water surface 82 and may be positioned vertically therewith.

In order to assure continual fiow of froth through the discharge conduit 78 the mixing cylinder 32 carries a water line 11% which has a discharge line 112 adjacent the froth deflector chute 76. The volume of water through the water line is controlled by the valve 114 thus assuring an accurate control of the discharge of the froth collected.

In addition to accurately separating out the froth, means are provided to individually separate sand and gangue into separate components. In order to achieve such separation, certain theoretical considerations must be taken into account. It can be shown that when a vessel such as a cylinder is partially filled with water and rotated about its vertical axis at a predetermined angular velocity, the surface of the water will assume the shape of a paraboloid. It may be shown that the equation for the paraboloid thus formed is as follows:

where H is the height of a particular point of the curve above the vertex of the paraboloid, r is the displacement of the point from the axis of the vertex, W is the angular velocity, and g is the acceleration due to gravity.

It will be apparent from this equation that the cross sectional shape of the water surface in a rotating container will be a function of the angular speed of rotation. For a given quantity of water in, for example, a cylindrical container, an increase in angular velocity increases the height attained by the water in the container.

This is illustrated in FIG. 4 wherein 3 parabolas are plotted utilizing the above formula for angular velocities of 60, 90, and 120 revolutions per minute, respectively.

For a submerged body rotating in the liquid mass between the curves 207 and 30-6 certain buoyant forces are at work. Assume in FIG. 4 that 116 represents a bubble. There are two forces acting on this bubble, one vertically and one horizontally. The force acting vertically is equal to W(H6H5)dA. The horizontal force acting on the bubble which tends to move the bubble to the left, as shown in FIG. 4, is equal to W(H4-H3)dA. In the above equations W represents the angular velocity, dA the cross sectional area of an incremental prism of the bubble parallel to the force referred to, and H-3, H-4, H-5, and H-6 represent the relative heights shown in FIG. 4.

It will be apparent from an examination of FIG. 4 that the second buoyant force tending to move the bubble to the left, as shown in FIG. 4, is considerably greater than the vertical buoyant force.

The horizontal force depends on the slope of the parabola for the difference in pressure head, while the vertical force depends on a difference in head equal to the diameter of the bubble. The horizontal buoyant force may be thus increased by increasing the angular velocity of the vessel which increases the slope of the parabolic curve describing the cross section of the surface of the water while at the same time this increase in velocity increases the difference in the pressure heads acting on the left and right sides of the bubble.

From these considerations it will be apparent that for a bubble of air lighter than the surrounding media, the forces will tend to move the bubble horizontally to the surface of the fluid. This tendency permits a rapid accumulation of froth at the surface where the Skimmers immediately remove it. However, for bodies which are heavier than the media surrounding it, that is the gangue and sand, different considerations must be applied.

Referring again to FIG. 4, assume that the vessel 14 is in cross section generally identical to the curve 2-07 represented by the number 118 and that this vessel is being rotated at revolutions per minute and has sufiicient water so that the surface thereof describes in cross section the curve 3-0-6 represented by 120. Consider now a small particle of rock 122 resting on the side of the vessel 14 and being held there by the centrifugal force resulting from the rotation of the vessel. Vector 124 represents the centrifugal force applied to the particle 122 in magnitude and direction. Vector 126 represents the component of the vector 124, normal to the tangent of the vessel wall at its point of contact. Vector 128 represents the resultant of vectors 124 and 126. Vector 128 is thus parallel to the tangent and indicates that the forces working on the particle 122 cause it to travel upward along the side of the vessel.

It will be obvious that there are other forces which might be considered, such as friction, but that these forces will be insignificant in comparison to the forces discussed.

Now referring again to FIG. 1, if the vessel 14 is rotated at such a speed so as to establish the water surface 82, from the above considerations it will be apparent that the froth will move to the surface and be collected by the Skimmers. Since slurry is being continuously introduced into the vessel from the bottom, it must discharge at a substantially constant rate from the top. While the slurry is moving upward, the particles heavier than water move outward toward the shell of the vessel, as explained above. Of course the larger the particle the more rapid the rate of outward migration, since it will be apparent that the centrifugal forces are a function of the mass of the particles. The rate of flow of the slurry decreases gradually toward the top of the vessel 14 because, as is apparent from an examination of FIG. 4, the cross sectional area of the water body is increased. At the same time the centrifugal force being applied to particles within the water body increases since the radius of the vessel is increased.

Near its top the vessel wall is flared outwardly as at 136 increasing substantially the effective radius. Secured to the walls of the mixing cylinder 32 is a vessel cover 132 which is curved outwardly and upwardly to form a space between the peripheral edge 134 of the vessel 14 and the peripheral edge 136 of the cover 132. Between the cover 132 and the walls of the vessel 14 is suspended the bafiie assembly 16. The baflie assembly 16 includes a baflie plate 140, one side of which is secured to the vessel 14 by an open web 142, the other side of which is secured to the cover 132 by the web 144. The lower edge 146 of the plate 140 is contoured generally to conform to the opposing wall of the vessel 14 while the opposite wall 148 is contoured to parallel the peripheral edge 136 of the cover 132.

At the juncture of the lower edge 146 and the opposite wall 148 the baffle plate 140 divides the rising water body into two portions, one of which flows into the channel 150 formed between the opposite wall 148 and the peripheral edge 136, the second of which flows into the channel 152 formed between the peripheral edge 134 of the vessel 14 and the lower edge 146 of the baffie plate 140.

The material moving into the channel 150 comprises principally water, unemulsified flotation reagent, small quantities of very fine rock and some froth which has not been removed by the skimmers 70. That portion of the mixture which passes into the channel 152 consists essentially of Water, the heavier sand and gangue and some moderate to fine particles. This mixture is forced to flow to the outer extremity of the upper portion of the vessel 14 where, because of the sudden increase in the effective radius of the vessel 14 the centrifugal forces are increased markedly.

At the outer extremity of the channel 152 a further division is made. Secured to the peripheral edge 134 of the vessel 14, and as the part of the baffle assembly 16, is a generally U-shaped outer baflle plate 154. The baffle plate 140 is provided with a projecting tongue 156 which forms in cooperation with the outer baffle plate 154 a generally S-shaped flow path for the mixture. As material proceeds up the channel 152 it enters into a precipitation chamber 158 and the heaviest particles are forced by the rotating forces toward the sand launder assembly 160, while the water and finer particles flow around the tongue 156 and up to the gangue launder assembly 162. The outer baifle plate 154 is secured to the body of the bafiie plate 140 by a web 164 and is further positioned by the 6 sand launder 166 and the gangue launder 162. By this construction the mixture is discharged from the vessel 14 in three separate portions, that portion proceeding up the channel 154) through the overflow launder assembly 166 and that portion proceeding up the channel 152 through the sand launder and the gangue launder 162.

Means are provided by which the size of the particles being discharged through the sand launder 160- and the gangue launder 162 may be externally controlled. Each of the assemblies 160 and 162 include an encircling plate 168 as par-t of the peripheral extremity of the vessel 14. This plate 168 contains a plurality of orifices 170 through which fluid may pass. Encircling the plate 168 is a movable port ring 172. The port ring is provided with a plurality of openings 174 capable of axially coinciding with the orifices 170-. The upper edge of the ring 172 is geared to mesh with a driving gear 176. The driving gear 176 is driven by a shaft 178 passing through the baflle plate 140, the outer baffle plate 154 and journalled within a bearing 188 carried by the vessel cover 132.

The shaft 178 is connected to a bell crank 182 which is in turn pinned to the piston rod 184 of a hydraulic cylinder 186. The hydraulic cylinder 186 is powered by suitable hydraulical lines which are connected to suitable hydraulic gland lines 190 carried by the mixing cylinder 32. The hydraulic lines are provided with conventional valvirrg suitable for controlling such a hydraulic system.

Since the assemblies 160 and 162 may be independently controlled, the volume of water passing through the separate orifices may be accurately controlled. Thus, if it is known that the material passing up the vessel 14 contains a large percentage of gangue and only a small percentage of ore bearing sand, the sand launder 160 may be completely closed and the gangue discharged through the gangue launder assembly 162. Encircling the individual launders 160, 162, and 166, are fluid receiving chutes 192 which carry the material discharged from the respective launders.

In the operation of the device thus described the vessel 14 is rotated at a preselected angular velocity. For the vessel shown in FIG. 1 the angular velocity is 90 revolutions per minute and the shape of the vessel in cross section conforms generally to the curve 118 in FIG. 4. The mixture of flotation reagent, water, finely ground particles of ore, sand and gangue are introduced into the slurry feed pipe 28. The hollow mixing shaft 34 is rotated so as to agitate the incoming slurry by suitable operation of the drive pulley 60. The skimmer assemblies 68 are positioned to conform to the water surface 82 by suitable activation of the elevator motors 96 through the motor switches 193. The skimmer motor 162 is started by throwing the skimmer switch 194 which causes the skimmer assemblies to rotate in a direction opposite of the direction of the rotation of the vessel 14. As the fluid falls through the mixing cylinder 32, air is introduced into the system through the air feed pipe 30. The slurry, as it falls down the mixing cylinder 32, is thoroughly agitated by the mixing blade 66 and aerated by air passing through the openings 64. The slurry enters the vessel by Way of the receiving chamber 48 and proceeds to fill the vessel, the water surface conforming generally to the simulated water surface 82. The skimmers 76 remove the froth which migrates to the surface 82, the froth being discharged through the conduits '78 and into the launder 86. If the froth is heavy, water is passed through the discharge lines 112 to facilitate removal of the froth. Since the operation is continuous, the removal of froth is continuous.

As the individual segments of fluid pass up the vessel they are intercepted by the bafiie assembly 16. The sand and gangue follow the channel 152 while the fine particles, water, and unflocculated flotation reagent pass up the channel 156. The material passing up the channel 150 is discharged through the overflow launder 166.

Depending on the size of the particles and the percentage of gangue as compared to sand, the sand launder assembly 160 and gangue launder assembly 162 are adjusted to provide flow paths leading to the fluid receiving chutes 192 by suitable activation of the bell crank 182. The material discharged through the sand launder 160, which accumulates in the precipitation chamber 158, may then be separated and reground for recycling, while the material discharged through the gangue launder 162 may be discarded.

It will be apparent that other means may be provided to control the size of the openings through which the sand and gangue are discharged. For example, FIG. shows a modification of the system previously described,

As shown in FIG. 5, the orifices 170 may be provided with a valve assembly 196. The valve assembly 196 includes a valve bonnet 198 fixed to a valve stem 200. A second valve bonnet 202 is slidably mounted on the valve stem 200. The valve stem slides in a valve guide 204. Encircling the valve stem 200 is a compression spring 206 which is seated on one side against the valve bonnet 198, and on the other against a pin and washer 208.

A rocker arm 210 bisects the spring 206 and is slidabl-y mounted on the valve stem 200. The rocker arm 210 is connected to a rod 212 which in turn is connected to cam wheel 214.

The cam Wheel 214 may be rotated by a motor (not shown) which drives the spur gear 216. The cam wheel is further provided with two oppositely disposed cams 220 which engage cam followers 222. The cam wheel 214- is driven at a constant speed and the valve bonnets oscillate in accordance with the cams and cam followers. The valve bonnet 198 is normally seated against the outside of the orifice 170. Sand or gangue accumulates within the chamber 224 and through the action of the rod 212 which is controlled by the cam, the bonnet 198 closes oif the interior of the orifice while the bonnet 202, moving from the seat, permits the accumulated sand to be discharged.

As soon as the cam followers pass the cams, the bonnet 198 once again seals the exterior of the orifice and persand or gangue to accumulate in the chamber 224. The speed with which this discharge can be made will be controlled by the speed at which the cam wheel is rotated.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details set forth, but my invention is of the full scope of the appended claims.

I claim:

1. A hydrodynamic ore concentrator for separating ore bearing froth, sand and gangue in an aqueous mixture comprising: a frame; a vessel'adapted to receive said mixture mounted on said frame; said vessel being generally parabolic in axial cross section and having an outwardly flared wall at the top thereof; power means for rotating said vessel at a predetermined constant speed to form a mixture surface within said vessel, said surface being generally parabolic in axial cross section; an operation control member carried by said frame and suspended within said vessel; a plurality of skimmer assemblies carried by said member, said assemblies each including a skimrner having a skimmer blade, and a froth deflecting chute; means carried by said member for vertically positioning said skimmer blades with respect to said surface; means carried by said vessel for rotating said skimmer assemblies in a direction opposed to that of the vessel; a vessel cover carried by said member, said cover cooperating with said flared wall to form a space therebetween; a bafiie assembly positioned between said flared Wall and said cover to divide said space into a plurality of channels; a sand launder assembly and a gangue launder assembly communicating with one of said channels, said launder assemblies each having a plurality of openings therein communicating with the exterior of said vessel and means for independently controlling the size of said openings.

2. A hydrodynamic ore concentrator for separating ore bearing froth, sand and gangue in an aqueous mixture comprising: a frame; a vessel adapted to receive said mixture mounted on said frame; said vessel being generally parabolic in axial cross section and having an outwardly flared wall at the top thereof; power means for rotating said vessel at a predetermined constant speed to form a mixture surface within said vessel, said surface being generally parabolic in axial cross section; an operation control member carried by said frame and suspended Within said vessel; a plurality of skimmer assemblies carried by said member, said assemblies each including a skimmer having a skimmer blade, and a froth deflecting chute; means carried by said member for vertically positioning said skimmer blades with respect to said surface; means carried by said vessel for rotating said skimmer assemblies in a direction opposed to that of the vessel; a vessel cover carried bywsaid member, said cover cooperating with said flared wall to form a space therebetween, a bafiie assembly positioned between said flared wall and said cover to divide said space into a plurality of channels; an overflow launder communicating with one of said channels; a sand launder assembly and a gangue launder assembly communicating with the second of said channels, each of said launder assemblies including an encircling plate having a plurality of orifices therethrough and a relatively movable port ring having a plurality of openings spaced tobe axially aligned with said orifices, said openings and orifices cooperating to form a'comrnunicating path between the interior and exterior ofsaid vessel; and means for moving said port ring relative to said plate to vary the size of said communicating path.

References Cited in the file of this patent UNITED STATES PATENTS 503,687 Seymour Aug. 22, 1893 648,711 Raasloif May 1, 1900 685,793 Raasloflf Nov. 5, 1 901 808,584 St. Pierre Dec. 26, 1905 974,075 King Oct. 25, 1910 1,373,743 Jones Apr. 5, 1921 1,549,913 Gale Aug. 18, 1925 1,751,982 Dunham Mar. 25, 1930 2,106,964 Wells Feb. 1, 1938 2,111,508 Jones Mar. 15, 1938 FOREIGN PATENTS 10,039 Australia Aug. 8, 1933 of 1932 104,368 Australia June 24, 1938

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