U.S. patent number 3,786,919 [Application Number 05/207,386] was granted by the patent office on 1974-01-22 for method and apparatus for concentrating ore pulps.
This patent grant is currently assigned to Ben H. Parker, Jr.. Invention is credited to Dewitt C. Deringer.
United States Patent |
3,786,919 |
Deringer |
January 22, 1974 |
METHOD AND APPARATUS FOR CONCENTRATING ORE PULPS
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.
Inventors: |
Deringer; Dewitt C. (Golden,
CO) |
Assignee: |
Parker, Jr.; Ben H. (Sao Paulo,
BR)
|
Family
ID: |
22770332 |
Appl.
No.: |
05/207,386 |
Filed: |
December 13, 1971 |
Current U.S.
Class: |
209/434; 494/27;
494/41; 494/66; 494/42 |
Current CPC
Class: |
B04B
5/00 (20130101); B04B 2005/0457 (20130101) |
Current International
Class: |
B04B
5/00 (20060101); B03b 003/10 () |
Field of
Search: |
;209/434,453
;233/1D,14R,12,27,28 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
112,205 |
|
Sep 1964 |
|
CS |
|
873,494 |
|
Jul 1961 |
|
GB |
|
Primary Examiner: Lutter; Frank W.
Assistant Examiner: Hill; Ralph J.
Attorney, Agent or Firm: Edwards et al.
Claims
What is claimed is:
1. 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;
gate-forming 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 tunnel-forming 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.
Description
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 2--2 of
FIG. 1, greatly enlarged;
FIG. 3 is a similar section taken along line 3--3 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 6--6 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
sehematically 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 20 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. It 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 70 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 open-topped tailings
compartment 108 as the centrifuge subassembly 44 rotates. While it
might appear from FIG. 1 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 FIG. 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 114 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 118 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 112 with short branch tubes 120a, 120b and
120c that connect directly into the tunnel through the wall of
tunnel-forming member 88. While supply line 112 and its branches
120a, 120b and 120c 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 drum-like 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 drum-like 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 88 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 60.degree. angle 144 either in half or, when using a conical
drum like that shown, the angles will be more like 25.degree. on
top and 35.degree. 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 146c and 146d, on the other hand, do not parallel the top
surface 142c 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 tunnel-forming 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 end-to-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 Ferrosilicon Recovery Heads 1.56 Concentrates 6.90 91.3
Tails 0.167
As far as operating speeds are concerned, the best results have
been achieved when the centrifugal force developed is upwards of 75
to 100 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.
* * * * *