Note: Descriptions are shown in the official language in which they were submitted.
2~S
This invention relates to a high intensity wet magnetic
separator capable of separating magnetic materials from non-
magnetic materials an~, more particularly, to such separator
having a vertically mounted rotor.
Magnetic separation has long been known as a valuable
technique in mineral separation and it has been particularly useful
in the separation of strongly magnetic materials from non-magnetic
materials. Although the greatest commercial use of magnetic
separators has been found in dry separation processes, recently new
types of magnetic separators have been very successfully used under
wet conditions.
In the past, magnetic separators have generally been in
the form of an axially rotatable drum having disposed interiorly
thereof a plurality of fixed magnets. These magnets are normally
placed in close proximity to the desired area of the interior
surface of the drum so that when magnetic particle-carrying
material is fed against the peripheral portion of the drum overlying
t~he fixed magnets, the magnetic particles adhere to the drum and
are then carried to a discharge position. The non-magnetic
20 material unaffected by the magnetic field normally is permitted
to fall under the force of gravity for separate collection. When
such equipment i5 employed for wet separating processes, a slurry
or pulp of the material to be separated either is fed to the
periphery of the drum in the same manner as dry material or, the
rotating drum may be partially submerged in a liquid slurry.
More recently for wet separation there has been developed
thc so-called high intensity wet magnetic separator and the most
commercially successful of these is the so-called "Jones
Separator". A typical design of the Jones separator is des-
30 cribed in U.S. Patent No. 3,326,37~, issued June 20, 1967. It
was of circular design with a series of vertically oriented
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grooved plates mounted in an annular rin~ which rotated hori-
zontally through alternating magnetic fields. In this manner a
magnetic field was introduced in the grooved plate sections as
they passed a magnetic pole, then reached a point of zero mag-
netic field between the poles of opposite polarity and a high
magnetic field at the next magnetic pole. A feed slurry was fed
into the grooved plates in the region of a magnetic pole so that
magnetic particles adhered to the plate walls. A water flush was
applied to help wash away the non-magnetic materials and then at
a point of low or zero magnetic field the magnetic particles were
released from the plates with the assistance of high pressure
water scouring. The magnetic and non-magnetic particles were
collected in separate launders. Magnetic pole pieces were usually
provided on opposite sides of the grooved plate sections and, in
order to obtain strong magnetic fields, these were usually in the
form of electromagnets.
Such flow through separators were designed with a hor~-
zontal rotor having a ring carrying the grooved plates and this
rotor was mounted for rotation on a vertical axle. From a mechan-
ical standpoint, particularly with very large machines, themounting bearings for such a vertical axle represent a significant
problem. Moreover, unless great care was taken to remove all
materials from the grooved plates during each cycle, there was a
tendency for some material to collect between the plates and thus
decrease the efficiency of the machlne. Also, unless great care
was taken to assure that all particulate material being separated
was below a certain minimum particle size, e.g. less than lmm,
other difficulties could be encountered since the oversized
particles would either remain on top of the grooved plate sec-
tion or become jammed between the plates.
One atte~pt to overcome some of these problems can be
found in Carpenter, u.S. Patent No. 3,375,925, issued April
2, 1968. It provides for a plurality of loose, unattached,
individually movable pole pieces, such as vertically posi-
tioned helical rods or ball bearings. However, it was found
in use that because of problems of rusting and the collec-
tion of deposits that within a quite short time these pole
pieces became fused together, thereby totally defeating the
purpose of having loose, unattached pole pieces.
Various attempts have also been made to provide a system
in which a rotor is mounted for rotation in a vertical
plane. Such a system is described in Bekhtle, U.S. Patent
No. 3,690,45~, issued September 12, 1972. Here again soft
iron balls are being used as induced pole pieces with the
idea being that these balls are free moving except when they
are under the influence of the magnetic field. In theory,
the balls are picked up in the magnetized region of each rot-
ation of the drum. However, the actual operation of these
machines has been observed in U.S.S.R. and it has been found
necessary to provide a separate elevator to deliver the
steel balls to an upper region where they are delivered by a
trough into contact with a magnetized region of the rotating
drum.
It is, therefore, the object of the present invention to
provide an improved design of wet magnetic separator which
will avoid the above difficulties.
SUMMARY OF THE INVENTION
According to this invention, the rotor of a rotary high
intensity wet magnetic separator is mounted on a horizontal
axis rather than the more conventional vertical axis. The
rotor has an annual separator portion formed by a pair of spaced
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~ nular side walls and a series of radial dividers made from non-
ma~gnetic material extend between these side walls thereby forming
a series of separate compartments magnetically isolated from each
other with open inner and outer ends. Induced pole pieces in the
form of magnetically permeable steel balls or grooved plates are
mounted within each compartment such that particulate material
can pass radially through the compartment. At least one magnet is
positioned immediately adjacent one of the annular side walls and
preferably there is a magnet adjacent each side wall. They can
10 be positioned at either an upper ar a lower region of the rotor
on generally the vertical diameter thereof for producing a magnetic
field within each compartment as it passes the magnet.
Inlet means are provided Eor feeding a slurry feed
downwardly into each compartment through an open end thereof while
the compartment is within the magnetic field of the magnet. The
feed inlet should be positioned at the leading edge of the magnetic
field and the magnetic particles immediately adhere to the induced
pole piece surfaces while non-magnetic particles pass through the
compartment. Collecting launders are positioned beneath the
20 compartments in this region to collect the non-magnetic particles
passing through.
Inlet means are also provided for delivering a first
flushing fluid downwardly into an upwardly facing compartment
opening beEore the compartment leaves the abovementloned magnetic
field. This is preferably in the form of a low pressure water
wash and it serves to remove non-magnetic material which is
trapped by the adhering magnetic particles. Collecting launders
are also positioned beneath the compartments in these regions
to separately collect a middlings product. This middlings
30 product may contain some magnetic particles which can be
recycled into the feed slurry.
Another inlet means is provided at a locatlon about
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1~0 from tlle magnet ~here the magnetic field is substantially
zero for delivery of a second flushing fluid to an upper open
end of a compartment. This ls preEerably in the form of high
pressure water spray or air-water spray which assists in removing
magnetic particles from the induced pole piece surfaces. Col-
lecting launders are also positioned beneath the compartments in
these regions to separately collect the magnetic products.
In order to accomodate the launders, etc. adjacent the
inner ends of the compartments, the annular separator portion is
connected to the rotor hub by means of an axially off-set web
portion. For example, the hub may be connected to one side wall
of the annular separator portion by means of a disc-like web
or radial spokes.
Since the magnets are adjacent the flat annular end
portions of the rotor, the magnet pole pieces can have flat
faces adjacent the rotor. The magnets can be placed on one or
both sides of the rotor and can be mounted at either an upper or
a lower region. Preferably, the magnets are mounted in pairs
with opposite poles on each side of the rotor and with the
20 opposite poles joined by a mild steel yoke to complete the mag-
netic circuit. The magnets can be either electromagnets or per-
manent magnets and the use of permanent magnets with this appa-
ratus is greatly simplified because of the flat pole end faces.
A particularly advantageous permanent magnet for this use is a
ceramic permanent magnet, such as that made from barium ferrite.
According to a preferred feature, a ceramic permanent magnet
can be used having on the same side north and south polarity.
For efficient operation, the non-magnetic dividers
should have considerable thickness, preferably an inch to
several inches. This provides for sufficient separation of
magnetic effects in individual compartments so that each
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compartment can function substantial]y in(lependent o~ adjacent
compartments.
The induced pole pieces can be made from magneticpermeable steel, e.g. mild steel, sta:inless steel (~00 series),
low carbon steel, etc., and take the form of grooved plates or
balls. Particularly when a permanent magnet having north and
south polarity on the same side is being used, grooved plates
are particularly advantageous for forming the induced pole pieces
since they prevent short circuiting of the magnetic flux. They
also permit unhindered flow of the solids and easier scouring
of magnetics by high pressure water. The induced pole pieces
are preferably characterized by a number oE sharp edges, corners
or surfaces causing convergence of the lines of force of the
effective magnetic field in which the pieces are disposed.
When discrete objects such as steel balls are used as
the induced pole pieces, these are held in postion in the separ-
ator compartments by inner and outer screens which allow the
particulate material to pass. By providing some free space in
each compartment, the balls will move during rotation of the
rotor and this has the effect of cleaning the balls-and thereby
preventing the balls from fusing together. This prevents any
plugging of the passages by the material moving through the
compartments and greatly lengthens the operational time without
a ~shut down.
As mentioned above, the magnets can be positioned
adjacent either an upper portion of the annular ring or a
lower portion of the ring. I~hen the magnets are located at
the upper portion of the ring, the slurry is fed through
the top outside arcuate region of the ring with the non-
magnetic material discharged through an inner arcuate region
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. . ., ~ ~
295
while the magnetics are attracted to ~he induced pole pieceswithin the separator compartment. When the compartment turns
to the lower position outside the magnetic field, the magnetic
particles are flushed out by water spray or air-water jet
entering from an inner arcuate region. Thus, it will be seen
that the flushing off of the magnetic particles is always
countercurrent to the feed flow. The high magnetic material
which may accumulate on the top of the induced pole pieces
during feeding of slurry will when the ring rotates 180 be in
a bottom position so that this accumulated material will be
flushed out first. Hence, any plugging of the separator by
highly magnetic particles is greatly reduced. Moreover, any
coarse material which is too large to pass through the spaces
between the induced pole pieces would be flushed away during
removal of the magnetic fraction.
This machine is capable of separating a wide variety
of different materlals and for instance, it may be used for
making a magnetic concentrate when the magnetic material is the
required product, e.g. concentration of relatively low magnetic
susceptibility ores such as hematite or chromite. Alternatively
it can be used for the collection and removal of magnetic
impurities from non-magnetic materials, e.g. removal of magnetic
contaminants, such as brolite, garnet or iron oxides, from
ceramics, chemicals, oils and steel plant effluents. It is
particularly advantageous for removing weakly magnetic con-
taminants from industrial effluents. For this purpose a
permanent magnet is uniquely suitable because it permits
extremely low operational costs. Also, any large contaminant
particles il~ such industrial effluents will not interfere with
the operation of the machine since they will always be removed
by the counterflow separation of the magnetic particles.
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llaving generally described the present invention,
more detailed illustration is given with reference to the
following drawings in which:
Figure 1 is a side elevation in partial section of
the separator;
Figure 2 is an end elevation of the separator;
Figure 3 is a vertical section through the annular
ring;
Figure 4 is a side elevation in partial section of an
alternate embodiment of the separator;
Figure 5 is a sectional view taken along line 5-5 of
Figure 4;
Figure 6 is a top plan view showing details of an
alternative embodiment;
Figure 7 is a sectional view through the embodiment
shown in Figure 6,
Figure 8 is a schematic view of Figure 6 showing flux
lines.
Figure 9 is a vertical section through a further em-
bodiment of the separator; and
Pigure 10 is a slde elevation in partial section of
the embodiment shown in Figure 9.
As will be seen from Figures 1, 2 and 3, this structure
has a rotor 10 mounted for rotation on a horizontal axle ll. The
rotor includes a pair of spaced annular mild steel plates 12
between which are fixed a series of radial truncated wedge-shaped
dividers 13 of non-magnetic material. thereby forming a series of
)z9s
magnetically isolated separators compartments.
These dividers can, for instance be made from "300
series" stainless steel, aluminum, copper, etc. The compart-
ments have open outer ends 32 and open inner ends 31. Spaced
inwardly from outer ends 32 are mesh screen portions 15 and
spaced inwardly from inner ends 31 are screen mesh portions 14.
These screens 14 and 15 retain therebetween a plurality of steel
balls 16. These steel balls can conveniently be ordinary ball
bearings having diameters ranging between 1/4" and 1". They
form a magnetlc collecting zone and represent induced pole pieces
when under the influence of a magnetic field.
As can be seen from Figure 3, the compartments are
not entlrely filled by the balls 16. Thus, at the slurry feeding
position the balls 16 are resting on outer screen 15 with a space
adjacent inner screen 14. Then, at the magnetic particle dis-
charge position the balls 16 have moved within the compartment so
that they are resting on inner screen 14 with a space adjacent
outer screen 15. This is an important feature in the use of balls
as induced pole pieces. The balls create a tortuous path for the
feed slurry passing through and this provides a very efficient
collecting of magnetic particles. However, if the balls are left
resting in this position during all stages of the process~they
quickly become bonded together by material from the feed slurry
which is trapped in the small crevices between the balls. With
the apparatus of this invention, the balls go through considerable
movement during each revolution of the rotor and this prevents any
build-up of material in crevices between adjacent balls. As a
result, the efficiency of the separat~on is improved from the out-
set and this high separation efficiency can be maintained for
long periods of operation.
,,,,~.,: ~
.~rr tl~.* . ~ _ g
~ dditional dividers are provided radially on each side
of the divlders 13, these being the outward divider 18 and the
inward divider 19. These can be simple radial plates as shown
in Figure 1 or they may be of triangular cross-section to assist
in the smooth delivery of slurry and scouring water into the
compartments.
The annular separator rLng section of the rotor is
mounted on a hub portion 20 which is offset such that there is a
clear area adjacent inner compartments ends 31. The hub 20 is
mounted on rotatbale shaft 11 which is in turn supported in a
bearing mount 21. This can be driven by an electrical motor (not
shown) by sprocket 22.
A permanent magnet assembly 23 is mounted at a lower
region of the rotor 10 with a north pole permanent magnet block
24 at one side and a south pole permanent magnet block 25 at the
other side. The pole faces are positioned to provide a small gap
between the pole faces and the sides of the rotor. A mild steel
yoke 26 joins the poles 24 and 25 while leaving a space 27 between
the yoke and the sides of the poles. The yoke serves to close the
magnetic circuit and thereby improve the flux intensity in the gap
between the poles. A hole 28 is provided in the yoke to allow
water and non-magnetic particles to pass through and deflector
plates 58 are mounted within space 27 for directing the material
emerging from the rotor through the hole 28.
A feed inlet pipe 29 is connected to a feeder head 30
which directs the feed into the compartments C via inner ends 31
at approximately the lowermost position in the rotation. The feed
should enter in the region of the leading edge of the magnet 23 and
as the feed passes down through the compartment C>the magnetic
particles adhere to the steel balls 16 while the liquid and non-
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magnetic material passes directly through the compartment and out
through outer end 32 where it is collected in a non-magnetic
collecting launder 33 and is carried away via conduit 34. A low
pressure water spray head 35 is also mounted adjacent open com-
partment end 31 in a lower region and this is arranged to supply
flushing water which helps to wash away non-magnetic material on
the magnetic particles as well as such material trapped by the
magnetic particles. This should be supplied while still under
the direct influence of the magnets 23 so that the flushing will
not remove magnetic particles. The flushing water is inthis
embodiment shown to also be collected by launder 33 but it will
be readily appreciated that if it is desired to separately collect
a middlings product, a separate launder and outlet can be provided
for this purpose below spray head 35.
At the side of the rotor diametrically opposite the
magnet 23 are high pressure water sprays or compressed air and
water jets 36. These are at a region of minimum influence from
the magnetic field created by the magnets 23 where the magnetic
particles can be easily removed from the steel balls 16. The
scouring water and removed magnetic particles are collected in
launder 56 and are carried away from the machine through conduit 57.
Figure 4 shows an alternative embodiment of the separator
in which the magnets 37 are located ad~acent an upper region of the
rotor diametrically opposite the location in Figure 1. These
magnets comprise a north pole permanent magnet block 38 at one
side of annular ring 10 and a corresponding south pole 39 at the
opposite side. The poles are joined by a mild steel yoke 40 with
a space 41 between the yoke and the sides of the magnets. Wi~h
this arrangement the feed inlet pipe 42 and feeder head'43 are
positioned at the top of the ring 10 at the leading edge of the
-- 11 --
- ~9~:);295
magnet with the head 43 extending through an opening in the yoke
whereby the feed is fed in through outer open ends and the
non-magnetic materials and water comes out through ~nner open
ends to be collected by launder 59 and conduit 60. The flus-
hing water head 53 is also positioned at the upper region of the
ring 10 within the fiel~ of the magnet 23 and extends through
the yoke so that this water passes in through outer end 32 and
out through inner end 31 to be collected by launder 59. If
desired,. the launder 59 can be replaced by a pair of side-by-side -
launders with one of these beneath feeder 43 to co.llect non-
magnetic particles and the other beneath flushing water head 53
to collect middlings. The scouring water or water-air high pres-
sure sprays 46 are in this embodiment positioned in the inner
region at the lower side of the rin.g 10 whereby the scouring
water is sprayed downwardly in through inner ends 31 and flows out
with the magnetic particles through outer end opening 32 and into
launder 44 where it is carried away by conduit 45.
With the wide dividers 13, it ma-y also be desirable to
provlde wedge-shaped flow deflectors adjacent the ends of the
dividers. For instance, they may include an outer ~edge-shaped
deflector 54 and an inner wedge-shaped deflector 55, as shown in
Figure 4. These are preferably made of the same material as the
dividers and serve to direct the flow into the compartment C, as
well as decreasing splashing and preventing build-up of material
on the ends of the dividers.
Figures 6, 7 and ~ show another embodiment of magnets
and induced pole pieces in which the magnets can be placed at
either an upper or a lower region of the ring 10. Once again the
magnets are placed on opposite sides of the ring 10 and each of
these magnets is in the form of a block of oriented barium ferr:..e.
Q '`
- 12 -
12~5
Each block is oriented such that one-half of the block is a south
pole 47 and the other half is a north pole ~8. A permeable steel
backing plate 49 is fixed to each magnetic block to complete the
magnetic circuit and this arrangement creates magnetic flux lines
as schematically illustrated in Figure 8. A magnetic arrangement
of this type can produce a magnetic circuit of about 8,000 Gauss
in the region between the induced pole pieces.
With this arrangement of magnets, in order to prevent
short-circuiting of the magnetic flux, it has been found to be
advantageous to utilize grooved plates 51 as the induced pole
pieces. Grooved plates are, of course, well known and are
illustrated in detail in U.S. Patent 3,830,367. The plates are
arranged in plate boxes separated by non-magnetic separators 50.
The material being separated flows down the gap 52 between the
plates 51, with the magnetics being collected on the grooved
faces of the plates. It will, of course, be understood that all
of the other components of the separator including the feeding
and washing devices and the product removal devices can be the
same as those described in Figures 1 to 5.
With special configuration of the permanent magnets as
shown in Figure 6, when the feed flows in through the feeding
head the magnetic particles come under the influence of the south
pole and orient themselves on the grooved plates under the south
pole influence. As the compartment moves into the influence of
the north pole, the magnetic particles reorient themselves under
this new influence and this reorientation of the magnetic particles
assists in the flushing away of non magnetic particles, particularly
those which may be trapped by the adhering magnetic particles.
Pigures 9 and 10 show a further embodiment with the
magnets at an upper region of the rotor. This arrangement has a
13 -
rotor mounted ~or rotation on a horizontal axle 61. The rotor
includes a mild steel plate member 62 fixed to the end of axle
61 and an annular ring 65 spaced from an outer portion of plate
member 62 so as to form an annular separator compartment 64
therebetween. This compartment has outwardly flared annular
portion 66 forming an enlarged entry 67. The compartment is
divided into a series of separate compartments by means of
radial dividers 71.
Each compartment contains steel balls 68 retained
within the compartment by means of a screen 69 at the outer
end and a screen 70 at the inner end. A pair of magnets 63 are
mounted at each side of the separator compartments and, as
shown in Figure 10, they are positioned on an incline down-
stream of the vertical centerline of the rotor.
The region below the magnets is enclosed by means
of an enclosure 72 having an outlet 73 at the bottom thereof.
Immediately above the magnets 63 is an inlet hood 74 within
which is mounted a feed inlet pipe 75.
Beneath the inlet 75 i5 non-magnetics collector
76 to receive the non-magnetic material which does not
adhere to the balls 68 within the field formed by the magnets
63. High pressure water sprays 77 are positioned to spray
downwardly through the separator compartments (from ~nner end
to outer end) when the compartments are remote from the
magnetic f ield. These sprays assist in washing the magnetics
from the steel balls 68 and out through discharge hole 73.
Additional water sprays may also be provided in the regions
of the magnets.
While the above detailed description has related
entirely to devices using magnets of the permanant type~ it
will be readily appreciated by those skilled in this field that
any of these permanent magnets can be readily replaced by electro-
magnets of known type, for example those shown in U.S.
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z~
Patent 3,830,367.
The invention is further illustrated by thefollowing examples:
Example 1
A test was carried out using a separator o~ the
design shown in Figs. 9 and 10. The feed was an uranium
ore containing brannerite and uraninlte as the principal
uranium ores. The ore was ground to -150 mesh ( U.S.
sieve) with 90.4% being -325 mesh. It contained 0.081%
10 U38
A slurry of this ground ore was formed con-
taining 25% solids and this was the ~eed stream to the
separator. The ore was separated into 13.7% magnetics
and 86.3% non-magnetics. The magnetics stream contained
0.493% U308, or 83.4% of the U3O8 contained In the feed-
stream The non-magnetics stream contained 0.0156% of
U308, or 16.6% of the U308 contained in the feedstream.
Example 2
The same separator used in Example 1 was
used to separate iron-bearing minerals from bauxi~e.
The ore being processed contained over 60% -10 micron
solids with an iron content of 9.4% (Fe203). The main
impurities were siderite, ferro-titanium oxides, iron
oxides, biotite, muscovite, garnet, etc.
This ore was fed to the separator as a slurry
containing 20% solids. The ore was separated into 14.0%
magnetics and 86.0% non-magnetics, with the magnetics
stream containing 48.2% Fe2O3 , or 71.7% of the Fe203
contained in the feed. The non-magnetics stream contained
30 only 3.1% Fe203, or 28.2% of the Fe2O3 contained in the feed.
_15
