Note: Descriptions are shown in the official language in which they were submitted.
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SEPARATING INTERMIXED MATERIALS OF DIFFERENT SPECIFIC GRAVITY
This invention relates to an apparatus and method for separating
intermixed materials of different specific gravity and in particular an
A arrangement employing a rotating bowl having discharge ports in the bowl
allowing heavier materials collecting in the bowl to discharge outwardly of the
bowl under centrifugal action for collection.
One example of an arrangement of this type is shown in U.S.
Patent 5,338,284 of the present inventor which discloses a centrifuge bowl
having a peripheral wall with the bowl being rotated about a longitudinal axis so
that the peripheral wall rotates about the axis and causes centrifugal force at
the peripheral wall to effect separation of materials passing over the peripheral
wall. The arrangement provides a plurality of axially arranged collection areas
each of which has a plurality of angularly spaced discharge ports so that the
materials collecting in the collection areas are discharged outwardly from the
bowl for collection. Pinch valves control the discharge.
Another arrangement is shown in International application
W093/1 3864 by McAlister.
It is one object of the present invention to provide improvements in
the above arrangement of the present inventor to enable an enhancement of
the efficiency of separation.
According to a first aspect of the invention there is provided a
method of separating intermixed particulate materials of different specific
gravity comprising:
providing a centrifuge bowl having a peripheral wall and an
open mouth;
rotating the bowl about a longitudinal axis so as to rotate
the peripheral wall around the axis;
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feeding the materials to the bowl so as to pass over the
peripheral wall and causing a heavier portion of the materials to collect on theperipheral wall while a lighter portion of the materials escapes over the open
mouth;
defining in the materials collected on the peripheral wall an
inner surface of the materials over which the fed materials pass;
defining on the peripheral wall at least one axially localized
area for collecting heavier materials while lighter materials pass over the areafor discharge;
defining at the area around the peripheral surface recess
means spaced outwardly of the inner surface;
providing at the area a plurality of angularly spaced
discharge ports at an outer surface of the recess means, each for allowing
materials collecting in the area to discharge outwardly from the peripheral wall;
collecting the outwardly discharge materials;
allowing the material discharging from the discharge port to
form a natural generally conical shape extending in both in angular and axial
directions which is substantially free from confinement by walls of the recess
means with an apex at the discharge port and a base of the conical shape at
the inner surface, the shape and depth of the recess means being arranged
relative to the angular spacing of the discharge ports such that bases at the
inner surface of the conical shapes of the discharge ports at least substantially
meet.
According to a second aspect of the invention there is provided a
method of separating intermixed particulate materials of different specific
gravity comprising:
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providing a centrifuge bowl having a peripheral wall and an
open mouth;
rotating the bowl about a longitudinal axis so as to rotate
the peripheral wall around the axis;
feeding the materials to the bowl so as to pass over the
peripheral wall and causing a heavier portion of the materials to collect on theperipheral wall while a lighter portion of the materials escapes over the open
mouth;
defining in the materials collected on the peripheral wall an
inner surface of the materials over which the fed materials pass;
defining on the peripheral wall at least one axially localized
area for collecting heavier materials while lighter materials pass over the areafor discharge;
defining at the area around the peripheral surface recess
means spaced outwardly of the inner surface;
providing at the area a plurality of angularly spaced
discharge ports at an outer surface of the recess means, each for allowing
materials collecting in the area to discharge outwardly from the peripheral wall;
collecting the outwardly discharge materials;
including providing for each discharge port a deflection
guide body and supporting the body radially inwardly of the discharge port;
including supporting the body so that materials pass on each
angularly spaced side of the body and also on each axially spaced side of the
body.
According to a third aspect of the invention there is provided a
method of separating intermixed particulate materials of different specific
gravity comprising:
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providing a centrifuge bowl having a peripheral wall and an
open mouth;
rotating the bowl about a longitudinal axis so as to rotate
the peripheral wall around the axis;
providing a feed material and feeding the feed material to
the bowl so as to pass over the peripheral wall and to cause a heavier portion
of the materials to collect on the peripheral wall while a remaining lighter
portion of the feed material escapes from the open mouth;
defining on the peripheral wall for rotation therewith at least
one first axially localized annular recess extending radially outwardly from theperipheral wall for collecting heavier materials while said lighter materials pass
over the first recess for discharge;
defining on the peripheral wall for rotation therewith at least
one second axially localized annular recess extending radially outwardly from
the peripheral wall for collecting heavier materials while said lighter materials
pass over the second recess for discharge, the second recess being
downstream of the first recess;
providing at the first and second recesses discharge means
at an outer surface of the recess, each for allowing materials collecting in therecess to discharge outwardly from the peripheral wall;
collecting the outwardly discharged materials from the first
recess;
collecting the outwardly discharged materials from the
second recess separately from the materials from the first recess and returning
the materials from the second recess to the feed material.
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According to a fourth aspect of the invention there is provided a
method of separating intermixed particulate materials of different specific
gravity comprising:
providing a centrifuge bowl having a peripheral wall and an
open mouth;
rotating the bowl about a longitudinal axis so as to rotate
the peripheral wall around the axis;
feeding the materials to the bowl so as to pass over the
peripheral wall and causing a heavier portion of the materials to collect on theperipheral wall while a lighter portion of the materials escapes over the open
mouth;
defining on the peripheral wall for rotation therewith at least
one first axially localized annular recess extending radially outwardly from theperipheral wall for collecting heavier materials while said lighter materials pass
over the first recess for discharge;
defining on the peripheral wall for rotation therewith at least
one second axially localized annular recess extending radially outwardly from
the peripheral wall for collecting heavier materials while said lighter materials
pass over the second recess for discharge, the second recess being
downstream of the first recess;
providing at the first and second recesses first and second
discharge means each at an outer surface of the respective recess, each for
allowing materials collecting in the recess to discharge outwardly from the
peripheral wall;
each of the first and second discharge means having valve
means for controlling discharge of the materials from the recess;
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collecting the outwardly discharged materials from the first
and second recesses;
and providing first and second control means for separately
controlling the valve means of the first and second recesses respectively so as
to provide for each of said first and second recesses different discharge
characteristics to provide different concentrations of the materials collected.
Embodiments of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a vertical cross-sectional view showing schematically a
first embodiment of centrifugal separator according to the present invention.
Figure 2 is a cross-sectional view along the lines 2-2 of Figure 1.
Figure 3 is a vertical cross-sectional view similar to that of Figure 1
on an enlarged scale.
Figure 4 is a vertical cross-section similar to that of Figure 1 of a
further embodiment of the invention showing some modifications and additions.
Figure 5 is an enlarged view of one part only of Figure 4.
Figure 6 is an enlarged view of another part only of Figure 4
The embodiment shown in Figures 1, 2 and 3 is modified relative
to the above mentioned U.S. Patent 5,338,284 of the present inventor which
shows a centrifugal separator having a plurality of rings defining therebetween
recesses with each recess having a plurality of angularly spaced discharge
nozzles. Each discharge nozzle is controlled by a pinch valve. The material
discharged from the pinch valves is collected.
Reference should be made to the above patent for further details
of the elements shown schematically in the drawings herein.
In Figures 1, 2 and 3, therefore, the apparatus comprises a
centrifuge bowl generally indicated at 10 including an inner bowl wall 11 and
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an outer housing 12 defining therebetween a space 13 for fluidization water
supplied through a hollow drive shaft 14 in a duct 15 within the shaft. The
drive shaft is connected to the bowl for co-rotation of the inner bowl and the
outer housing with the shaft. The shaft is mounted on bearings 16 and is
driven by a drive system generally indicated at 17.
The inner bowl is shaped to define a frusto conical base portion
18, a first annular recess 19 and a second annular recess 20. This shape is
therefore modified relative to the previous arrangement in that there are only
two recesses and the base portion includes the frusto-conical wall extending
from a flat base 21 onto which the feed materials are discharged by a feed duct
22. The materials thus are spread outwardly by engagement with the flat base
21 and engage onto the frusto-conical wall 18 so as to turn and move up the
wall of the bowl. The base and frusto-conical wall are covered by a liner layer
23. The liner layer 23 also engages into the recesses 19 and 20. The recesses
19 and 20 are each of generally rectangular cross section as shown in Figure 1
but the liner material is shaped so that it becomes thicker toward a base of therecess thus shaping the recess into a generally V shape. In some embodiments
the liner layer can be omitted or of constant thickness so that the recesses arerectangular as shown in the left-hand side of figure 1.
The bowl in the area of the recesses is formed by two annular
discs 24 and 25 connected by a cylindrical base wall 26. The liner material 23
as shown in the right-hand side of figure 1 is of constant thickness so as to
follow the side walls 25 and 24 part way through their depth and then
increases in thickness to form the V shape. In figure 3, the liner material is of
increasing thickness through the whole of the recess so as to form constantly
diverging walls.
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The base walls 26 of the recesses are spaced from a cylindrical
wall 28 of the outer housing so as to provide a space therebetween into which
the fluidizing liquid or water can penetrate for injection through two or three
rows of openings 30 in the base wall 26 into the interior of the recess.
The base 26 of each recess has a number of discharge ports 29 at
angularly spaced positions around the recess as best shown in Figure 2. These
discharge ports are of the general shape shown in the above patent except that
the ports do not include injection openings for injection of water into the
recess. The ports comprise simply discharge ports with a longitudinal duct
which diverges in shape as previously described with a pinch valve at the outer
end for controlling the amount of material discharged.
As shown in Figure 2, the injection openings 30 are arranged to be
inclined relative to a radius of the bowl so as to tend to inject the liquid
tangentially around the bowl to effect the fluidizing action on the materials inthe recess.
The recesses are modified relative to the above prior patent in that
the depth of the recess is significantly increased and in addition a flow guide
body 32 is provided in association with each of the discharge ports 29. Each
flow guide body 32 is positioned radially inwardly of the respective discharge
port so as to set the location spaced inwardly from the port but Iying within the
recess. Various shapes of guide body can be used, but in the arrangement
shown the guide body 32 is spherical. Each guide body 32 supported by a pair
of support arms 33 and 34 extending vertically upwardly from the guide body.
The support arms 33 and 34 are coupled to the liner 23 by engagement into a
pair of slots 34A formed at the top and bottom side walls respectively of the
recess so that the guide body 32 can be moved radially outwardly of the bowl
into the slots and is held in position by the centrifugal forces on the guide body
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and by the frictional engagement of the arms in the slots. The radial position of
the guide body can be adjusted by bending the arms.
The separation of the materials therefore occurs generally at the
mouth of the recesses and between the walls 24 25. The separation occurs at
an inner surface of the material indicated at 35 in which the heavier materials
collect into the recesses between the wall 24 and 25. The lighter materials
pass over the collection area defined by the recesses and over the open mouth
of the bowl to a collection system schematically indicated at 36. The heavier
materials collect within each of the recesses for movement outwardly through
the discharge ports 29 for collection of the heavier materials within a collection
system schematically indicated at 37.
The position of the guide bodies immediately forward of the
discharge ports acts to support the material radially inward of the guide body to
prevent that material from pressing radially outwardly on the discharge port dueto the high centrifugal force. It will be appreciated, in the absence of the guide
bodies all the centrifugal force on the "~ate~ial will press the material against
the discharge port providing a very high force at that location. The guide body
takes away some of that force and transfers the force to the bowl wall while
the material can slip around the guide body both at top and bottom as shown
in figure 3 and on the sides as shown in figure 2.
The discharge zone of each discharge port is therefore generally
conical with an apex at the discharge port at an axis of the cone extending
radially inwardly of the bowl. The cone thus diverges outwardly around the
guide body with the angle of the cone being dependent upon the slippage of
the material which is related to its repose angle. In addition the material is
fluidized by injection of the water through the openings 30 tending to prevent
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the high centrifugal force on the material from drying the material and thus
forming an immovable wedge of material in front of the discharge port.
The depth of the recess is however modified relative to the
previous arrangement in that as shown in Figure 2 the cone of the discharge
zone in front of each discharge port diverges so that the bases 35A, 35B of the
cones intersect at the inner surface 35 of the material. In addition the cone isarranged as shown in Figure 1 so that the sides 35C cone of the discharge
zone extends to a position adjacent the walls 24 and 25. The discharge zone
therefore defines a pattern on the inner surface 35 which is substantially
circular with those circular discharge patterns overlapping so as to draw
material from substantially the whole of the inner surface at the recesses 19
and 20. The separation of the material at the inner surface therefore provides alayer of the heavier material on the inner surface which is then collected and
discharged gradually outwardly as the material is discharged from the discharge
ports 29.
In one example, therefore, the axial height of each recess is of the
order of 6 inches and the radial depth of the recesses is of the order of 6
inches and these dimensions are arranged so that they provide approximately
the arrangement of the discharge zone as shown.
The shaping of the liner to substantially follow the shape of the
discharge cone as shown on the right hand side of Figure 1 assists in avoiding
stationary material being located within the recesses. However the fluidization
of the material in the recess by the injection openings 30 provides a gradual
migration of the material around the recess to enter the discharge zone of each
discharge port. However the main effect of the discharge ports is to collect thematerial from the inner surface 35 and to gradually move that material
outwardly to the discharge port. The guide body 32 assists in increasing the
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angle of the discharge cone so as to increase the dimension of the discharge
pattern at the inner surface.
It will be noted from Figure 3 that the inner surface 35 of the
material within the recess is defined by inner edges 24A and 25A of the side
walls 24 and 25 and that the inner surface at the recess 19 is thus frusto-
conical with a cone angle following or substantially equal to that of the insidesurface of the portion 18 of the bowl. The length of the portion 18 is arranged
so that it is sufficient that the layer of the materials from the feed tube 22 is
smoothed by the centrifugal action to lie as a layer 22A which is of
substantially constant thickness over the upper part of the wall portion 18 as
the materials 22A approach the inner surface 35. At the position where the
materials enter the area of the inner surface 35, the materials are thus moving
directly parallel to the inner surface 35 to avoid gouging of the material within
the recess. The separation therefore occurs as the materials flow smoothly
over the inner surface 35 with an exchange of heavier materials for lighter
materials in the conventional manner of a centrifuge. The heavier materials
thus collect within the recess and the lighter pass in the layer 22A to the nextrecess for further separation and final discharge from the mouth.
In some cases it may be desirable to add a perforated layer of a
rigid material as indicated at 35X Iying in the plane of the inner surface 35.
Thus the perforated material 35X can be formed from expanded metal or similar
perforated rigid material forming a frusto-conical section which is attached to
the inner edges 24A and 25A to hold the perforated section in place. This
perforated section therefore assists in guiding the material flow 22A over the
inner surface 35 and to yet further avoid gouging, that is the penetration of the
material flow into the recess. Such gouging, if it occurred, would cause
extraction of the heavier materials from the recess and return of those heavier
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materials into the material flow 22A so that such heavier materials would be
lost.
Turning now to Figure 4, this is modified relative to the cross
section shown in Figure 1 to show further detail of the construction of the
housing and launders 36A and the shaft 14. Further, the cross section is
modified to show further details of the ducts 29A supplying control air to the
pinch valves 42. Thus each row of pinch valves includes a supply duct 42A
which communicates actuating air to the respective row of pinch valves and
that duct 42A is supplied through the supply ducts 29A from a manifold
arrangement 29B provided at the shaft 14.
The arrangement in Figure 4 is yet further modified by the addition
of a third recess 50 downstream of the recesses 19 and 20. The third recess
50 is substantially identical to the first two recesses and is of a slightly
increased diameter matching the increase in diameter between the recesses 19
and 20 due to the conical shape of the bowl wall.
As previously described, the material discharged from the recesses
19 and 20 is collected in a launder 37A and the tailings materials discharged
over the mouth of the bowl is collected in the launder 36A. In the embodiment
shown in Figure 4 an additional launder 51 is provided which collects the
material solely from the recess 50 and supplies this material to a pump 52.
Downstream of the pump 52 is provided a manually operable valve 52A which
can be operated to return the material to the feed 53 entering the feed duct 22
or to direct the material to the concentrate collection. In an alternative
arrangement, the bowl may have only two recesses with the concentrate from
the second recess being collected separately from the first and passed to the
pump for selected direction to the feed or to the concentrate depending upon
the grade of material being processed.
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In this way the third (or second) concentrating ring or recess 50 is
provided as a scavenger ring. The content of this ring is continuously
discharged through the pinch valves into the launder 51 and is from that
launder pumped, on operation of the valve 52A back into the feed inlet of the
machine. The concentrate grade of the scavenger ring is not adequate to
discharge into the concentrate stream from the launder 37A but contains some
values worth recovering. Thus recirculating the discharge from the recess 50
into the in feed of the machine will move the values from the scavenger ring
into one of the two lower rings for later discharge as concentrate.
A yet further modification shown in Figure 4 relates to the
mounting of the support ring 34 which, instead of being mounted by axially
extending support elements 38 is instead supported by radially extending
support elements 38A which extend from the ring radially outwardly therefrom
as shown at 38A in Figure 2 so as to hold the ring at the required position
midway up the recess and centered around the central axis of the bowl. The
number of support arms 38A can be selected in accordance with structural
requirements but in general there will be four such support arms positioned
intermediate the discharge ports and therefore intermediate the guide body 32.
Turning now to Figures 4, 5 and 6, the details of the control
system to the valves 42 are shown. Thus the valves 42 of the channel 50 are
controlled commonly by a fluid supply duct 60 which is separate from the fluid
supply duct 61 of the channels 19 and 20. This allows the valves 42 of the
channel 50 to be operated in a pulsed manner with a rate of the pulses greater
than that of the valves of the channels 19 and 20 so as to pull off an increasedamount of material. Thus the total period that the valves are open for the
channel 50 is greater than the total period that the valves open for the channels
19 and 20 to provide an increase in the amount of material discharged. In
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some circumstances this can be obtained not by increasing the rate of the
pulses but by increasing the period of the pulses.
The pulsing of the valves of course acts to discharge the material
in sequential portions. All of the valves of a respective one of the channels are
open simultaneously by the provision of fluid pulses in the respective supply
duct 60, 61.
In Figure 5, the connection of the supply ducts 60 and 61 to a hub
62 of the shaft is shown. The shaft is thus formed by three concentric tubes
63, 64 and 65. Between the tubes 63 and 64 is provided a first annular duct
66. Between the tubes 65 and 64 is provided a second annular duct 67 and
inside the innermost tube 65 is provided a third duct 68. The duct 61 is
connected to the duct 68 by one or more radially extending pipes 69 which
extend radially through the hub 62. Similarly the duct 67 is connected to the
duct 60 by a plurality of radially extending pipes 70 which are axially offset
from the pipes 69. Thus the pipes 69 connect with the duct 68 at the very end
of the duct. The duct 68 terminates at a position spaced axially from the end
of the tube 65 since the tube 64 ends at a position spaced axially from the end
of the tube 65. The hub 62 includes a block 71 which has a threaded bore 72
receiving an end of the tube 64. The block 71 further includes a counter bore
73 into which the tube 65 extends with the counterbore providing an end part
of the duct 68 which connects with the ducts 69. The block 71 is received in
an end of the tube 63 and acts to close the end of the tube 63. At the lower
end of the block 71 is provided a plurality of ducts 74 which extend radially
outwardly from connection with the annular duct 66 within the tube 63.
The hub 62 further includes a sleeve 75 and an outer sleeve 76.
The sleeve 75 is directly connected around the outside of the tube 63. The
sleeve 76 is sp~ced outwardly and defines an annular channel connected with
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the ducts 74 and extending therefrom to an opening in a base wall 77 of the
outer bowl or jacket. Water supplied through the duct 66 of the shaft thus
passes outwardly through the radial duct 74 and through the annular channel
between the sleeve 75 and 76 to and through the base 77 for fluidizing the
bowl as previously described.
The tube 63 defines the outer most surface of the shaft which is
carried in the bearings 16 as previously described. The tube 63 projects
through the lowermost bearing 16 and into engagement with the pulley 17 and
terminates at the pulley 17. The tube 63 has threaded into it at its lower end arotary union 79 for injecting water through the rotary union into the rotating
shaft defined by the tube 63. The rotary union is a commercially available item
conventionally used on rotary elements of this type for injecting a fluid into the
rotating shaft. In this case the tubes 64 and 65 extend through the rotary
union 79 for connection to a second rotary union 80 for supply of fluid to the
ducts 67 and 68. The rotary union 79 includes a male thread 82 at its lower
end onto which is attached a cap 83 which closes the lower end of the rotary
union for sealing the lower end and preventing the escape of water from the
lower end of the rotary union. The cap 83 includes a spring biased seal 84
biased downwardly by the spring 85 to provide engagement of sealing member
86 against a sealing washer 87 at a lower end of the cap 83. The washer 87
is held in place by a bolted end plate 88 screw fastened to the body of the cap
83.
The tubes 63, 64 and 65 forming the shaft all rotate commonly
with the hub 62 in driving rotation of the bowl. The rotary union 79 is
stationary so that the tube 63 rotates within the stationary rotary union.
The second rotary union 80 includes a cap portion 89 which is
attached to the lower ends of the tubes 64 and 65 for rotation therewith. Thus
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the cap portion 89 includes a female screw thread 90 receiving a male thread
of the tube 64 therein. Seals 91 and 92 prevent the escape of fluid to the
outside of the tubes 64 and 65 respectively. The cap 89 includes a central
duct 93 communicating with the duct 68. The cap further includes a plurality
of ducts 94 arranged at radially spaced positions around the central duct 93
and communicating with a counter bore section 95 within the end cap 89
communicating with the duct 67. The end cap 89 is bolted by bolts 96 to the
lower part of the rotary union indicated at 97. The lower part of the rotary
union 80 is a commercially available item having an upper cap portion 98 which
rotates with the cap 89 and a lower portion which remains stationary and is
connected to suitable supply ducts (not shown) for communicating the fluid
into the ducts 93 and 94.
The single shaft as shown, therefore, provides the communication
of the fluidizing water around the outer most one of the annular channels
together with communication of control fluid through the central circular
channel and through the inner annular channel. If required, a yet further tube
can be provided in the construction of the shaft so as to provide four ducts
coaxially arranged each inside the next. Such four ducts are then used to
provide the fluidizing liquid and to provide three sets of control fluid each for
controlling a respective one of the valves sets of the channels 19, 20 and 50.
This arrangement allows each of the channels to be individually tailored in
regard to its discharge characteristics to the amount of concentrate collecting
in that particular channel.
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