US 3786919 A
This invention relates to a centrifugal ore concentrator characterized by a spirally wound tunnel-forming member wound about a rotatable core into which an ore pulp is introduced. As the ore pulp gravitates, or is preferably forced, through the whirling spiral, the heavy minerals that have migrated to the outside of the tunnel under the influence of the centrifugal action are drawn off and separated from the lighter gangue particles that are similarly drawn off from the inside. The invention also encompasses the novel method of concentrating ore pulps which comprises feeding the pulp through a rotating spirally disposed tunnel with a pulsating action, dividing the stream and drawing off the heavier material from the outside and the lighter material from the inside.
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Description (OCR text may contain errors)
United States Patent [1 1 Deringer [4 1 Jan. 22, 1974 1 1 METHOD AND APPARATUS FOR CONCENTRATING ORE PULPS  Inventor: Dewitt C. Deringer, Golden, C010.
22 Filed: Dec. 13, 1971 211 App]. No.: 207,386
Primary Examiner-Frank W. Lutter Assistant ExaminerRalph J. Hill Attorney, Agent, or FirmEdwards et a1.
57 ABSTRACT This invention relates to a centrifugal ore concentrator characterized by a spirally Wound tunnel-forming member wound about a rotatable core into which an ore pulp is introduced. As the ore pulp gravitates, or is preferably forced, through the whirling spiral, the heavy minerals that have migrated to the outside of the tunnel under the influence of the centrifugal action are drawn off and separated from the lighter gangue particles that are similarly drawn off from the inside. The invention also encompasses the novel method of concentrating ore pulps which comprises feeding the pulp through a rotating spirally disposed tunnel with a pulsating action, dividing the stream and drawing off the heavier material from the outside and the lighter material from the inside.
5 Claims, 6 Drawing Figures PATENTED JAN 2 2 I974 SHEEIl M3 FIG.|
INVENTOR DEWITT c. BY %lf RINGER I I l TI PATENTEB JAN22I974 SHEEI 2 0? 3 INVENTOR DEVITT ERINGER "i W TORlXE METHOD AND APPARATUS FOR CONCENTRATING ORE PULPS Ore pulps or slimes containing mineral values and gangue particles of similar density have, for a long time, presented the oredressing engineers with a problem of considerable difficulty. Gravity separation has proven to be only nominally effective as a means for concentrating ores containing particulate materials of nearly the same size and density and it has long been suspected that centrifugal separation would be the better method; however, up to now, no commercially acceptable method or apparatus based upon this principal has been found. In fact, over 40 years ago, namely in 1929, the United States Bureau of Mines published Technical Paper 457 in which they suggested that centrifugal separation should prove better than gravity concentration with the difficult slimes and pulpy ones but, despite numerous attempts to implement this suggestion on the part of eminent mining engineers, few, if any, have proven to be much more than a laboratory curiosity.
It has now been found in accordance with the teaching of the instant invention that an effective method and apparatus for concentrating ores employing centrifugal separation techniques can, in fact, be achieved which are both efficient and practical. The unique apparatus involves a whirling spirally wound coil containing one, or more, gates dividing the stream into inner and outer branches which are directed into separate reservoirs or launders. In the preferred embodiment of the apparatus, the slurry is constantly diluted as it migrates through the coil in order to maintain its fluidity and prevent the solids from packing along the tunnel walls. The mobility of the mixture is preferably maintained by forcing it through the system with a pulsating action which tends to inhibit the build-up of solids while, at the same time, breaking up any dams that do form.
It is, therefore, the principal object of the present invention to provide a novel and improved ore concentrator.
A second objective of the within-described invention is the provision of a centrifugal concentrator especially suited for use in the separation of finely divided particulate materials of similar density.
Another object of the invention herein disclosed and claimed is to provide a centrifugal ore concentration method wherein the raw material is force-fed through the system with a pulsating action.
Still another objective of the invention forming the subject matter hereof is to provide a method and apparatus for continuously concentrating ore pulps and slimes that utilize the novel technique of diluting the raw material as it migrates through the system.
An additional object is the provision of a centrifugal ore concentrator in which the concentrates and tails are continuously deposited in separate stationary launders from which they can be withdrawn for further processing or disposal even while the coil is still turning.
Further objects are to provide a centrifugal ore concentrator that is versatile, efficient, compact, reliable, relatively inexpensive, easy to operate, and one that is readily adapted for use with ores of various types and characteristics.
Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follows, and in which:
FIG. 1 is a view, partly in elevation and partly in diametrical section showing the centrifugal ore concentration apparatus of the present invention, certain portions thereof having been broken away to conserve space while the pump that delivers the raw material has been illustrated schematically to a reduced scale;
FIG. 2 is a somewhat diagrammatic section taken along line 22 of FIG. 1, greatly enlarged;
FIG. 3 is a similar section taken along line 33 of FIG. 1 to the same scale as FIG. 2;
FIG. 4 is an enlarged fragmentary detail showing the rotating frusto-conical core of the concentrator encircled by the spirally wound tunnel-forming member and associated waterline, portions of the latter having been broken away to conserve space;
FIG. 5 is a still further enlarged fragmentary view showing a section of the segmented tunnel-forming member that includes a gate to divide the stream and means connected to the outside branch for separating the heavier mineral values from the lighter gangue material; and,
FIG. 6 is a section taken along line 66 of FIG. 5 and to the same scale as the latter.
Referring next to the drawings for a detailed description of the present invention and, initially, to FIG. 1 for this purpose, reference numeral 10 has been chosen to designate the concentrator in its entirety while numeral 12 similarly denotes a raw material pump operatively associated therewith. Conduit 14 is connectable to a supply of the raw material which requires beneficiation and it delivers same to the inlet of pump 12 or, alternatively, directly to the inlet of the concentrator in instances where no pump is used. Under some circumstances it is possible to effect a meaningful concentration by relying upon gravity flow alone of the raw ore through the whirling convolutions of the concentrator 10, however, certainly the best results are realized when the raw material is force-fed through the unit by means of pump 12. In fact, in accordance with the teaching of the preferred beneficiation method, the raw pulp or slime is pumped with a pulsating type of flow through the system rather than at a constant or near constant flow rate. In other words, pump 12 is preferably one of several commercially-available pulsating types capable of handling slurries with a substantial proportion of solids suspended therein while, at the same time, delivering same in intermittent surges at intervals of relatively short, but nevertheless discreet, duration. It has been found that a pulsating flow like that described above serves to both prevent the build-up of solids along the walls of the convoluted tunnel and, simultaneously, break down any dams or other obstruction that may have begun to form.
The outlet 16 of the pump is connected to the inlet 18 of the concentrator which terminates in an endcap 20 that mounts atop the cover 22 that carries the packing gland 24 within which hollow shaft 26 is sealed for rotation. Gland 24 has been shown somewhat schematically as the details of its construction form no part of the present invention and such units are well known in the prior art. Shaft 26 is journalled in shaft bearing 28 that is mounted on top of the main frame 30 within cover 22. Shaft 26 continues in one form or another all the way through the main frame and out the bottom of crossframe member 32 where a second journal 34 therefor is located. As the shaft opens into area 36 beneath crossframe member 32 in the frame, it connects into a packing gland 38 through which water from a water line 40 enters the system.
Back up at the top again, it will be seen that the inlet to the concentrator discharges into a fluid-tight sealed chamber 42 defined by endcap and cover 22. As this chamber fills, the slurry is forced under pressure into hollow shaft 26 preparatory to entering the helicoidal convolutions of the centrifuge subassembly that has been designated in its entirety by reference numeral 44. Note in this connection that slurry does not pass directly into hollow shaft 26 from the pump, but instead, enters chamber 42 located therebetween which functions as a small surge tank to reduce the shock loads imposed by the repeated slugs of raw material that are fed into the system by pump 12 while, at the same time, maintaining the desired fluctuations in fluid pressure that have been characterized herein as pulsating flow.
A pulley 46 mounted on the upper section 48 of shaft 26 is connected to a second pulley 50 on shaft 52 of motor 54 by belt 56. Motor 54 is supported outside the main frame on motor mount 58 and provides the drive for rotating the centrifuge. In the particular form shown, shaft 26 is in three sections, an upper section 48, a middle section 60 and a lower section 62, the adjoining ends of which are provided with flange-type shaft couplings 66. It is middle section 60 that carries the centrifuge subassembly 44 to which all the remaining figures of the drawing are directed and which will be described in detail presently. Flow between the upper and lower sections of shaft 26 bypasses most of center section 60 and is directed instead through the centrifuge subassembly.
Still referring to FIG. 1, mounted on the main frame in encircling relation to the lower end of the centrifuge subassembly is a stationary concentrate launder subassembly 68. The latter subassembly has a large central opening 70 through which shaft 26 passes and within which it and the centrifuge subassembly rotate. In the particular form illustrated, the portion of subsassembly 68 located between inner and outer concentric cylindrical walls 72 and 74 is divided into a pair of upwardly opening annular concentrate-receiving compartments 76 and 78 by partition wall 80 disposed therebetween and sloping bottom wall 82. The latter wall slopes downwardly off in both directions to a diametrically opposed point where a pair of drains 84 and 86 are located, one of which opens into each of the two compartments and provides the means by which the concentrates are removed therefrom.
As illustrated herein, the helicoidal convolutions of the tunnel-forming member 88 of the centrifuge subassembly 44 are tapped into at two different points by concentrate drain tubes 90 and 92 whose function it is to draw off concentrates flowing along the outside wall of the tunnel 94. These two tubes turn right along with the other elements of the centrifuge and their discharge ends terminate, respectively, within compartments 76 and 78. lt is obvious that by placing the axis of concentric annular compartments 76 and 78 essentially coincident with the axis of rotation of the centrifuge subassembly that the concentrate drain tubes can move around within their respective compartments without contacting the walls thereof. By drawing off the concentrates at two or more points as shown, the heaviest of the fractions comes off first or the farthest upstream while the next heaviest exists through tube 92 into the inside compartment 78, and so on. If the apparatus is like that shown in FIG. 1 where only two taps are made and a two-compartment launder catches the concentrates, the second tap 92 should be made well along toward the end of the tunnel-forming member 88 where the ultimate achievable separation will take place. Since the initial fraction will, in all likelihood, be considerably larger than the second or any subsequent one except under very rare circumstances, outside compartment 76, or whichever one receives the first fraction is preferably the largest.
Extending down through the central opening in the concentrate launder subassembly 68 is the tailings drain tube 96 which empties into the tailings launder 98 disposed within the main frame. Tailings launder 98 also has a central opening 100 therein through which passes the lower section 62 of shaft 26. The outer and inner cylindrical walls 102 and 104 of the tailings launder cooperate with one another and with the sloping bottom wall 106 to define a single tailings compartment 108 having a drain opening 110 at its lowest point. As was the case with the concentrate drain tubes 90 and 92, the discharge end of the tailings drain tube whirls around within the confines of the stationary opentopped tailings compartment 108 as the centrifuge subassembly 44 rotates. While it might appear from FIG. I that the concentrate compartment drains empty directly into the tailings compartment therebeneath, this is obviously not the case and appropriate drain lines (not shown) are connected into these drain openings to direct the products wherever needed for further processing.
Before leaving P16. 1 it will be seen that the stream of water that enters the lower end of shaft 26 through packing gland 38, emerges near the bottom of the middle section 60 and is fed into an external supply line 112 which rotates with said shaft inside the central opening 70 in the concentrate launder 68 before spiralling upwardly around the drum-like support 114 that carries the tunnel-forming member 88. As will appear presently in connection with FIG. 4, support 1 14 is actually a greatly enlarged portion of shaft 26 located intermediate the flanged ends of its center section 60. Neither the raw material nor the water coming up from the bottom enters this drum-like support because the short stubshaft portions 116 and l 18 at the ends of the center section have blind adjacent ends (see FIG. 4). Thus, external supply line 112 bypasses the interior of supporting drum 114 and spirals upwardly around the outside thereof between the descending convolutions of the tunnel-forming member 88.
While the water circulating through the coils of supply line 112 ascends around the outside of drum-like support 114, it actually enters the system and moves in concurrent flow relation to the slurry descending through the tunnel 94. This is accomplished by tapping into supply line 1 12 with short branch tubes 120a, 120b and 1200 that connect directly into the tunnel through the wall of tunnel-forming member 88. While supply line 112 and its branches 120a, 1201; and 120a are intended for use in diluting the slurry or pulp as it moves through the coils of the centrifuge, it can also be used for the purpose of introducing other ingredients into the system should the need therefor arise. For example, in the event of blockage, one may wish to introduce an appropriate solvent into the unit. The overall efficiency of the system may even be enhanced by introducing such chemical additives as wetting agents, agglomerating agents, and the like directly into the moving slurry.
Next, with reference to FIGS. 2 and 3, the functional structures within centrifuge subassembly 44 will be set forth in detail. First, looking at FIG. 2 it will be seen that the middle section 60 of shaft 26 has an opening 122 in the wall thereof above the top 124 of the drumlike support 114 that defines one of the plugs blocking the latter. Connected into this opening in a manner to receive the raw material therefrom and deliver same to the inlet of the tunnel-forming member 88 is a curved delivery tube 126. A short tubular coupling 128 forms the fluid-tight junction between adjacent ends of the latter.
Branch 120a of the water line 112 has been shown connected into the tunnel in the tunnel-forming member 88 immediately downstream of its inlet although this location is not critical and it could just as well enter the system elsewhere. The concentrate drain tube 90 that carries off the first and heaviest of the fractions is shown located well downstream of the inlet in FIG. 2.
In FIG. 3, the manner in which the discharge end of the tunnel-forming member is fastened into the tailings drain tube by means of a simple male-female telescopic connection 130 is clearly shown. Immediately upstream of this connection is the gate 132 that divides the stream and allows the heaviest of the fractions remaining therein to be drawn off through tube 92 connected into concentrate discharge branch 134. As previously mentioned, there may be several such concentrate drains positioned to remove concentrate fractions from various points throughout the centrifugal system.
Next, referring to FIG. 4, it will be seen that drumlike support 114 is essentially a frustum of a right cone defined by conical wall 136, the upper and lower ends of which are capped by top and bottom walls 124 and 138. While entirely adequate separation would certainly take place if the support member were cylindrical rather than frusto-conical, the latter shape has the advantage of steadily increasing the centrifugal force acting upon the descending stream of material being treated due to its gradually moving farther out from the axis of rotation. In a system like the one shown where the heaviest and most easily separated fraction is removed about half way through the centrifuge, it is highly desirable to exert a greater centrifugal force near the downstream end of the system where the differentials one has to work with are narrower and further separation becomes more difficult for this reason. Finally, with reference to FIGS. 5 and 6, it can be seen that one specific type of tunnel-forming means 38 that can be employed to advantage is made up in segmented form from a plurality of individual molded ceramic blocks 140 having a triangularly shaped opening 142 therein that defines tunnel 94 when said blocks are connected together in end-to-end relation as shown. The use of ceramic blocks in preference to pipe or tubing of some sort has the advantage of making it possible to provide the tunnel with hard glazed walls better able to resist the abrading action of the solid particles suspended in the pulsating pulp stream. Along this same line, a glazed tunnel wall is less likely to resist the flow of material to a point where solids will collect along the outside thereof. Also, while the pulps and slurries being concentrated in the system are seldom corrosive, the flushing fluids used to clean same may well be.
The main tunnel-forming blocks 140 are all identical to one another and each has a more or less trapazoidal cross section having an equilateral triangular opening therein. One side of the triangular opening 142a is essentially parallel to the adjacent conical surface of the drum-like support 114 while the angle 144 opposite said side is located on the outside of the tunnel. In fact, tests have shown that angle 144 should either be bisected by a line normal to the axis of drum rotation or, preferably, such a line will divide this angle in such a way that the smaller of the two included angles is on top. For instance, with an equilateral triangular tunnel like that shown, the line normal to the axis will divide angle 144 either in half or, when using a conical drum like that shown, the angles will be more like 25 on top and 35 on the bottom. If, on the other hand, the lesser of the two angles is on the bottom, the concentrates tend to stay up along the top of the tunnel and miss the gate 132 and associated discharge branch. As illustrated, the exterior wall 146a on the inside of the spiral adjacent drum 114 is also essentially vertical and parallel to tunnel wall 142a as is the case with the lower exterior wall 146b and bottom tunnel wall 142b. The top exterior surfaces 1460 and 146d, on the other hand, do not parallel the top surface l42c of the tunnel, but instead, they cooperate therewith to encompass a thickened wall 148 having a passage 150 therethrough as shown. When the blocks are aligned to form the coils of the spiral, passages 150 are also aligned and, in fact, are for the purpose of receiving a cable or rod which, upon being threaded therethrough, holds the blocks in assembled helix-forming relation.
At each point in the convolutions of the tunnelforming member 88 where concentrates are to be drawn off, two specially designed blocks 140x and 140y are used which cooperate with one another to define gate 132 and concentrate discharge branch 134 as shown. The seams between the blocks may, if desired, be caulked to reduce leakage and pressure losses and, in addition, the coils are preferably wrapped from endto-end with a fibreglass tape 152 which is sufficiently resilient to allow the individual blocks to adjust relative to one another so that their adjacent ends mate properly. The wrapping also tends to seal the joints between blocks and, of course, insulate the coils. Obviously, ordinary helicoidal tubing could be substituted for the tunnel-forming element shown and the system would still function as intended.
Some idea of the capabilities of the unit described above can be appreciated from the fact that a slurry containing minus 200 mesh marble and minus 325 mesh ferrosilicon after being concentrated therein gave the following results:
Percent Fer-rosilicon Recovery Heads 1 .56 Concentrates 6.90 9 l .3 Tails 0. l 67 As far as operating speeds are concerned, the best results have been achieved when the centrifugal force developed is upwards of to times that of gravity although, obviously, there is no sharply defined range and lesser speeds will still prove quite effective in terms of bringing about a centrifugal separation of the mineral values from the gangue.
The improved ore concentration method comprises pumping the slurry under pressure with a pulsating motion through one or more coils of a helicoidal tunnel while whirling same, dividing the stream into two branches downstream of the inlet and recovering the outside stream.
What is claimed is:
l. The centrifugal ore concentrator which comprises: tunnel-forming means defining a helicoidal passage having an inlet at one end and an outlet at the other mounted for rotation about a vertically-disposed axis; pump means connected to deliver an ore pulp under pressure into the inlet of the tunnel-forming means while it is rotating; drive means connected to the tunnel-forming means operative upon actuation to rotate same at a speed sufficient to bring about centrifugal separation of the heavier of two solid fractions suspended in the ore pulp circulating therethrough; gateforming means disposed within the tunnel-forming means downstream of the inlet for dividing the ore pulp stream into an inside branch in which are suspended the major portion of the lighter of the two solid fractions and an outside branch containing primarily the heavier solid fraction; means defining a concentrate launder disposed adjacent the outlet of the tunnelforming means; tubular means for removing the outside branch of the pulp stream from said tunnel-forming means and transferring same to the concentrate launder connected into the tunnel-forming means adjacent the gate-forming means for rotation therewith; and, a fluid line rotatable with the tunnel-forming means connected to introduce fluids therein at one or more points, said fluid means being connectable to a stationary supply of fluid under pressure.
2. The centrifugal concentrator as set forth in claim 1 in which: a shaft having a hollow inlet end, a hollow outlet end and a drum-like enlargement intermediate its ends is journalled for rotation in vertically disposed relation; a main fluid line is carried by the drum-like enlargement for rotation therewith; one or more branch fluid lines interconnect said main line and the interior of said tunnel-forming means; and, in which the hollow outlet end of the shaft is connected to receive fluid under pressure from a stationary source thereof while rotating and deliver same to the main fluid line.
3. The method of separating the heavier particulate fraction from a fluid suspension containing both heavy and light fractions which comprises: pumping the slurry under pressure with an intermittent pulsating motion through the coils of a whirling helicoidal passage, dividing the slurry stream into two branches, one flowing along the inside wall of the passage and the other flowing along the outside wall thereof, tapping off the outside branch and collecting same.
4. The method as set forth in claim 4 which includes the steps of dividing the stream at more than one place within the passage, tapping off the outside branch immediately downstream of each such division, and collecting the outside branches while keeping same separate from one another.
5. The method as set forth in claim 4 which includes the step of continuously diluting the slurry while it circulates through the passage.