Note: Descriptions are shown in the official language in which they were submitted.
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CONTINUOUS CENTRIFUGAL SEPARATOR OF HEAVIER PARTICULATE
MATERIALS FROM LIGHT PARTICULATE MATERIALS IN A SLURRY
The invention relates to the continuous centrifugal separation of
heavier particulate materials from light in particulate materials in a slurry
of the
materials, in which the slurry is passed over the peripheral wall of the
centrifuge
bowl for collection of the heavier materials on the wall of the bowl with a
plurality of
discharge openings at angularly spaced positions around the wall to allow the
heavier materials to discharge from the bowl while the slurry runs
continuously
through the bowl.
BACKGROUND OF THE INVENTION
The present inventor has the following patents which disclose
machines of this general type and features which relate to such machines:
US 5,222,933 Issued December 13, 1994
US 5,338,284 Issued August 16, 1994
US 5,586,965 Issued December 24, 1996
US 5,601,523 Issued February 11, 1997
US 5,601,524 Issued February 11, 1997
US 4,608,040 Issued August 26, 1986
US 6,149,572 Published November 21, 2000
In addition to the above patents of the present inventor, the following
patents by other inventors show machines and features of a similar nature:
McAllister US 5,462,513 December 31, 1995
Classicon UK 2,133,722 August 1, 1984
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Burnell US 4,981,219 January 1, 1991
MacNicol Australia 17487/34 May 8, 1934
Australia 22055/35 April 2, 1935
Maclssaac US 1,882,389 October 11, 1932
Loison US 3,823,869 July 16, 1974
Telle DT 1,632,324 October 29, 1970
Knelson 284 discloses a machine of this general type which is
intended to operate continuously in the sense that the feed slurry is supplied
continuously to the centrifuge bowl while the discharge of heavier materials
collected
on the wall of the bowl is effected intermittently using a pinch valve at each
discharge opening.
Knelson 523, 524, 965 and 572 disclose improvements in the above
machine all of which have contributed to an improved functional machine.
Knelson 933 discloses a batch machine which operates intermittently
and must be halted regularly for the collection of the heavier materials
through a
discharge opening at the base of the bowl. There is no continuous discharge of
the
heavier materials through discharge openings and the heavier materials is
therefore
collected in the bowl for intermittent or batch processing.
Knelson 040 discloses a particular arrangement of the fluidizing
injection openings which are conventional in an arrangement of this type.
McAllister discloses a continuous discharge machine which also uses
pinch valves at a series of discharge openings around a collection zone of the
bowl.
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MacNicol in the old two Australian patents discloses a particular bowl
arrangement with injection openings at the base of a series of axially spaced
riffles
for collection of materials of the batch processing within the riffles.
Telle discloses a de-watering system for extracting water from
particulate materials in which the particulate materials are collected on the
wall of a
centrifuge bowl and discharged outwardly through discharge ducts each of which
has a pinch valve for controlling the discharge of the particulate materials.
De-
watering systems are of a different type from the particulate separation
machines
with which the present invention is concerned.
Maclssaac discloses a machine for separating particulate materials in
which the heavier materials are collected on the wall of the bowl and
intermittently
discharged by opening valves located inside the bowl.
Classicon discloses a separation system for different particulate
materials in which there are series of actually spaced discharged outlets each
of
which can be opened and closed by a valve arrangements.
Loison discloses a de-watering device for separating liquid from a solid
in which the solids are collected outwardly of the bowl and are discharged by
periodically opening a valve arrangement.
Burnell discloses an apparatus for separating different particles
including a series of angularly spaced pockets each of which converges to a
discharge duct through which the heavier materials are discharged on a
continuous
basis.
SUMMARY OF THE INVENTION
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It is one object of the present invention to provide an improved method
for separating particulate materials of different density in which the feed is
substantially continuous and the heavier materials are discharged through
discharge
openings arranged on the peripheral wall.
According to the invention there is provided a method of separating a
slurry containing 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 the materials to separate such that a heavier portion of the
materials
collects on the peripheral wall while a lighter portion of the materials in
the slurry
escapes over the open mouth;
defining on the peripheral wall at least one axially localized annular
recess for collecting the heavier portion of the materials;
defining in the recess an upper side wall and a lower side wall
converging to a base interconnecting the side walls;
providing at the recess a plurality of angularly spaced discharge ports
each for allowing materials collecting in the recess to discharge outwardly
from the
peripheral wall, each discharge port being located with a mouth at the base;
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providing for each discharge port a valve operable for closing the port
for preventing discharge of collecting materials and for opening the port, and
periodically operating the valve during the separation of the materials to
allow said
discharge;
5 collecting the outwardly discharge materials;
injecting fluidizing liquid into the recess through a plurality of fluid
injection ports arranged at angularly spaced positions around the recess for
fluidizing the material in the recess;
providing in the recess a bed of movable bodies free to move within
the recess and located inwardly of the fluid injection ports and inwardly of
the
discharge ports;
the movable bodies being larger than the particles and shaped to as to
define interstices between the bodies so as to allow the particles to pass
therebetween;
and confining the movable bodies within the recess.
Preferably the movable bodies are generally spherical so that they may
be termed as balls. However a spherical shape is not essential and other
shapes
may be used and the term "beads" used herein is not intended to be limited to
spherical shapes.
Preferably the movable bodies or beads are confined in the recess by
a radially inner screen and a radially outer screen.
Preferably the inner screen and the outer screen are connected to form
an insert member separate from the recess so as to be removable therefrom.
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However the screens or other constraining members may be formed as part of the
structure of the recess. While screens are preferred since these can confine
the
beads regardless of the dimensions of the beads, other retaining members can
be
used which have larger openings to allow the passage of the materials while
retaining the beads in the recess.
Preferably the inner screen and the outer screen are connected by two
side walls of the insert member spaced by a width of the recess.
Preferably the side walls lie in radial planes of the axis of the bowl and
preferably the recess has the side walls thereof each of which has a portion
lying in
a radial plane of the bowl at the side walls of the insert member. This is
designed so
that it follows the shape of the recess at this point so that the recess is
closed by the
screens and layer of beads. However the shape and arrangement of the insert
member may be different from that of the recess provided that it remains in
place
during operation.
Preferably the recess has at least one side wall thereof which has a
portion which is removable to allow ready release of the insert member for
replacement when worn or when a different characteristic is required.
Preferably at least one of the side walls has an opening therein
through which the bodies can be fed into the insert member for loading and for
replacement of the beads by beads of a different size, density or material.
Preferably the bed of the movable bodies is arranged relative to the
fluid injection so that at least some of the beads are moved radially inwardly
of the
bowl by inward fluid movement when the discharge ports are closed and at least
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some of the bodies are moved radially outwardly of the bowl by outward fluid
movement when the discharge ports are opened.
Preferably the bed of movable bodies comprises sufficient of the
bodies to provide a single layer of the bodies substantially in contact with
one
another within the recess. Although more layers of the beads can be provided
to
enhance the diffusion effect of the discharge at the separation surface.
The invention is also directed to the centrifuge apparatus for use in
separating a slurry containing intermixed particulate materials of different
specific
gravity comprising:
a centrifuge bowl having a peripheral wall and an open mouth;
the bowl being mounted for rotation about a longitudinal axis so as to
rotate the peripheral wall around the axis;
the bowl being arranged for feeding the materials to the bowl so as to
pass over the peripheral wall and causing the materials to separate such that
a
heavier portion of the materials collects on the peripheral wall while a
lighter portion
of the materials in the slurry escapes over the open mouth;
at least one axially localized annular recess on the peripheral wall for
collecting the heavier portion of the materials;
the recess having an upper side wall and a lower side wall converging
to a base interconnecting the side walls;
a plurality of angularly spaced discharge ports at the recess each for
allowing materials collecting in the recess to discharge outwardly from the
peripheral
wall, each discharge port being located with a mouth at the base;
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each discharge port having a valve operable for closing the port for
preventing discharge of collecting materials and for opening the port and
arranged
for periodically operating the valve during the separation of the materials to
allow
said discharge;
a plurality of fluid injection ports for injecting fluidizing liquid into the
recess arranged at angularly spaced positions around the recess for fluidizing
the
material in the recess;
a bed of movable bodies in the recess free to move within the recess
and located inwardly of the fluid injection ports and inwardly of the
discharge ports;
the movable bodies being larger than the particles and shaped to as to
define interstices between the bodies so as to allow the particles to pass
therebetween;
and confining members mounted in the recess for confining the
movable bodies within the recess.
The invention also includes as a separate aspect the insert member for
use in a centrifuge apparatus as defined above where the insert member
comprises:
a bed of movable bodies in the recess free to move within the recess
and located inwardly of the fluid injection ports and inwardly of the
discharge ports;
the movable bodies being larger than the particles and shaped to as to
define interstices between the bodies so as to allow the particles to pass
therebetween;
and confining members including a radially inner screen and a radially
outer screen connected by two side walls of the insert member spaced by a
width of
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the recess and arranged to be mounted in the recess for confining the movable
bodies within the recess.
The embodiment disclosed hereinafter is therefore an annular or
circular diffusion ring that fits inside the recess. The diffusion ring is
made of two
screens mounted on a steel ring with space in between the screens. There are
slots
on the top steel ring to allow the "beads" to be loaded into the space between
the
two screens. The size of the screens and the distance between them is variable
depending on the size of the machine. The size and specific properties of the
beads
are also variable. The beads may be glass spheres with a diameter of 5 mm. The
beads can be made of various materials such as ceramics, steel, plastic, etc.
The
amount of beads added, in terms of the resulting bed thickness, is also a
variable.
For example, there may be just enough beads to provide a thickness of one bead
diameter.
The purpose of this modification is to provide:
1. A "live reciprocating screen" for recovery of smaller high density
particles.
2. An even distribution of fluidization water to the concentrating
surface.
3. A "ragging bed" which oscillates inwardly and outwardly as the
valves are closed and opened and thus assists in fluidizing and separating the
particles within the recess rather than just at the mouth of the recess.
The machine is operated in such a manner that the fluidization water
flow rate is set so that the beads are lifted away from the back screen and
are
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essentially fluid or floating. The surface screen is essentially there so that
these
beads do not get blown out of the recess and into the tails stream. The pinch
valves
are opened at regular intervals in exactly the same manner as the operating
procedure described in the above US patent 6,149,572. The open and close times
5 are variable and allows for a variable amount of mass to be pulled to the
concentrate.
When the pinch valves are closed, the fluidization water lifts the bead
bed away from the back screen. When the pinch valves open, the bead bed
collapses but also pulls the concentrated bed formed on the surface of the
screen to
10 be collapse through the interstitial spaces between the beads. A jigging
effect also
takes place as high density particles (in the ore) would tend to collapse
faster than
the lower density beads. This is where the concept of using beads of different
materials (i.e. different specific gravities) may be useful. It may allow the
differential
recovery of different mineral species in the ore.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a vertical cross sectional view through a bowl of a
continuous variable discharge separation system, which is taken from US Patent
6,149,572 above to show the basic construction of the apparatus with which the
present invention is concerned.
Figure 2 is a vertical cross sectional view similar to that of Figure 1
through the same bowl with the insert member of the present invention added.
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Figure 3 is a vertical cross sectional view similar to that of Figure 2 on
an enlarged scale showing only one side insert member.
Figure 4 is an isometric view of the insert member alone.
In the drawings like characters of reference indicate corresponding
parts in the different figures.
DETAILED DESCRIPTION
The centrifugal separation apparatus as shown in Figure 1, and
described in more detail in the above US patent to which reference should be
made
if further detail is required, comprises a bowl generally indicated at 10
having a base
11 and an open mouth 12. A feed duct 13 comprises a vertical pipe mounted on a
central axis 14 of the bowl for feeding a slurry 15 downwardly onto the base
11 of
the bowl. The bowl 10 includes a peripheral wall 16 so that the slurry moving
outwardly to the peripheral wall under centrifugal forces passes over the
peripheral
wall for collection of heavier materials in a pair of collection recesses 17
and 18 and
for discharge of lighter materials and water over the open mouth 12.
The material collecting in the recesses 17 and 18 is discharged radially
outwardly through a series of discharge ports at spaced positions around the
recess.
Each discharge port forms part of a discharge port and valve assembly 19.
The materials discharged from the open mouth is collected within a
first launder 20 for collection and transportation to a discharge area. The
heavier
materials collected within the recess 17 is discharged from the assembly 19
and
collected within a middle launder 21A. Similarly the material discharged from
the
recess 18 is collected within a third launder 21 B.
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The bowl 10 is mounted on a shaft 22 for rotation about the axis 14.
US Patent 5,222,933 discloses further details of the base of the bowl
including a base plate 11A and a bottom discharge opening 11 B.
Reference is made to Knelson US patents 5,601,523, 5,601,524 and
W097/02894 (mentioned above) all of which disclose various constructional
features
of the above machine. In particular construction of the shaft is shown in US
Patent
5,601,524. Further the general shape of the bowl including a lower frusto-
conical
portion 16A which directs the feed material across the recesses 17 and 18 is
shown
in US Patent 5,586,965. The further patents can be referred to for further
details of
the construction if required.
Each recess has a plurality of fluid injection openings 24 for injecting
fluidizing water into the recess adjacent the base of the recess so the
fluidizing water
can flow through the recess and mix with the materials in the recess as
described in
the prior patents of Knelson.
A hub 22A carries the bowl and is mounted on a shaft 22 is of the type
generally shown in US Patent 5,601,524 for supply of fluidizing water through
the
hollow shaft to the supply ducts.
In general the shaft 22 is connected to a water supply coupling at the
lower end (not shown) so that water is supplied through a hollow interior of
the shaft
for connection to ducts which extend outwardly to the couplings for supplying
the
injection openings 24.
The general shape of the bowl including the two recesses 17 and 18
together with the first conical section 16 is substantially as described in US
Patent
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5,586,965. However the bowl as shown herein is modified relative to the bowl
of the
above patent in that it includes a bottom discharge opening 11 B connecting to
ducts
1 and a base plate 11A above the bottom discharge opening.
In normal operation of the bowl as shown herein, the feed material is
separated so that the heavier particles collect within the recesses and the
lighter
particles and water escape over the mouth 12. The heavier particles are then
discharged by periodic opening of the pinch valves to allow release of a plug
of
collected heavier particles. The tapered shape of the inside surface ensures
that the
plug can freely escape into the valve section and through the valve section to
the
exterior launder for collection.
As best shown in Figure 2, the recesses are modified to include an
additional insert member 30 which is mounted in the recess at the mouth of the
recess. The recess is thus defined by an inner edge 31 on the bottom side wall
32
and an inner edge 33 on the top side wall 34. Each of the side walls includes
a first
portion lying in a radial plane of the axis 14. The upper side wall 34
includes the
radial portion 35 which can be removed to allow insertion of the annular
member 30
at that position. Each of the side walls from its radial portion includes an
inwardly
converging portion 36 which extends to a base 37 at which is located the port
19A of
the discharge valve assembly 19 which includes the valve 19B.
At the base or at the bottom of the side wall is provided the injection
openings 24 for injection of fluidizing water into the recess.
The annular insert member 30 comprises an inner screen 38 and an
outer screen 39 both of which are formed into a cylindrical shape with the
outer
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screen 39 having a larger diameter. The inner and outer screens are connected
by
top and bottom side walls 40 and 41 respectively which connect the screens and
provide a hollow interior 42 between the screens and between the sidewalls.
The
top sidewall 40 includes an opening 43 by which beads 44 can be inserted into
the
hollow interior 42. Thus the insert member provides a confining cavity for
receiving
a plurality of beads forming a bed within the insert member and confined by
the
insert member. The beads are thus held within the recess by the inner and
outer
screens at a position radially inward of the injection and discharge ports and
radially
outward of the mouth of the recess defined by the cylindrical surface
containing the
inside edges 31 and 33. The inside screen 38 is located substantially at the
inside
surface of the recess or mouth of the recess so that separation of the
materials from
the material flowing over the mouth of the recesses occurs at or just inside
the
screen 38.
The balls or beads are located within the hollow interior of the insert
member and are held in position within the recess so that the beads can move
freely
within the hollow interior 42 under the fluid forces generated by the
discharge
through the discharge port and the injection through the inlet port.
As the beads have a larger diameter than the particles they are more
affected by fluid flow so that they move inwardly and outwardly under fluid
flow
regardless of the relative densities. The beads do not fill the cavity 42 so
that the
beads are free to move between the inner and outer screens. The beads are
shown
in a single layer but there may be provided additional beads to provide a
greater
number of layers. The beads will of course tend to move and float within the
cavity.
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However the beads will tend to migrate between the inner and outer screens.
When
there is a net tendency of the beads to migrate radially outwardly, they will
spread
over the outer screen to form a bed. Similarly when there is a net flow
inwardly from
the injection water fluidizing the recess, with the valve closed, the beads
will tend to
5 float onto the inner screen 38 again forming a bed thereon.
The effect of the beads is that it tends to spread the flow from the
recess into the discharge port when the valve is opened, over a larger area at
the
mouth of the recess. Thus instead of a shallow or narrow cone being formed of
material collapsing into the discharge port, the cone may extend outwardly to
the
10 bed of beads but then is diffused by the beads. Thus radially inwardly of
the beads,
the bed within the recess tends to collapse toward the discharge port through
the
bed as a smoothly moving zone of collapse over the full area of the bed
inwardly of
the beads. Thus, where the concentration is occurring primarily at the mouth
of the
recess, the hole of the material collecting at the mouth of the recess moves
radially
15 outwardly toward the discharge port.
Furthermore the balls tend to move through the material within the
container 42 so as to fluidize the materials within that area and thus assist
in
separating heavier from lighter particles within that zone. Thus the heavier
particles
tend to move past or between the beads more quickly to the screen 39 for
discharge
through the discharge port while lighter particles tend to remain adjacent the
screen
38 and thus can be moved outwardly when the outward flow recommences as the
valve is closed.
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Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without departing from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
