Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a magnetic separator for
minerals separation and to methods of minerals separation.
The invention is particularly concerned with a separation
system in which the material to be separated is allowed to fall
freely past a high strength magnet. The relatively magnetic matter-
tat is attracted towards the magnet and the relatively non-magnetic
material continues in a relatively straight path. Splitter members
may be used to separate the two streams.
One problem which has been encountered is that if all the
material falls in a relatively low magnetic field and the magnetic
material which is attracted to the magnet only reaches the high
field region when it has already been separated from the non-
magnetic. On the other hand, if the material all falls closely
adjacent the magnet wall, then the non-magnetic material falls down
with the magnetic material and there is not sufficient relative
movement of the magnetic material to achieve separation
A magnetic separator in accordance with this invention
solves this problem by providing means at or closely adjacent the
inner wall of the separation channel and extending down over at
least a part of -the portion of the separation channel which extends
past the magnet to divert the particulate material to be separated
substantially horizontally away from the magnet.
The invention provides a method of separating relatively
magnetic particles from relatively non-magnetic particles comprise
in allowing a mixture of the magnetic and non-magnetic particles
to fall, under at least the influence of gravity, in a -three
dimensional stream in a common path closely adjacent to a wall of a
channel nearest a magnet which is arranged and designed to produce
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a strong magnetic field force in a horizontal direction, the
horizontal component being greater than that of the vertical come
potent which is less than that of gravity, the free fall of the
particles being interrupted as they pass adjacent the magnet to
cause them to move away Eros the magnet thereafter the magnetic
particles move back -towards the magnet whereas the non-magnetic
particles are not drawn away from their diverted path.
From another aspect, the invention provides a magnetic
separator comprising a super-conducting magnet and at least one
particle separation channel adjacent the magnet, means for feeding
particles in a stream closely adjacent the wall of the channel
nearest the magnet, and means at or adjacent the said wall of the
channel and extending down over at least a par-t of the portion of
-the separator channel which extends past the magnet to divert the
particles away from the magnet.
The diversion means may comprise a bump, hump or ridge,
preferably having a smooth upper surface so as to avoid remixing
of the material. A sharp step causes mineral to be bounced at
random and this may cause a degradation in the quality of spear-
anion. Several bumps or humps may be provided one above
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the other.
alternatively the diversion means may take the shape ova chute or "ski" ramp having a profile extending in the
direction of free fall, outwardly from the magnet, followed by
a neolced potion.
he use of the particle diversion means enables the ore
to be fed adjacent the inner wall of the separation channel
i.e. that nearest the magnet and in the region of maximum field
strength for the channel. Some separation takes place above the
said diversion means, but this to limited. When the stream of
particles is diverted by the said means, away from the magnet,
the non-magnetic particle are thrown out well clear of the
magnet and then continue to fall in their diverted path. the
magnetic particles on the other hand are drawn back towards the
magnet immediately after being diverted and thereafter follow
the wall of the channel.
The two streams then pass on either side of an
appropriately positioned splitter plate.
he magnet for the separator is preferably cryogenic
and may have a circular coil or coils or may be the linear magnet
described and claimed in our co-pending Application No.
filed simultaneously herewith.
typically, the stream of ore is 3 to 6 mm in thickness
and the ridge or bump 24 projects 4 to 10 my from the surface
of the wall. It is desirable -that the shape is smooth on the
upper side 80 as to avoid remixing of the mineral. A sharp
step causes mineral to be bounced at random and this may cause a
degradation in the quality of separation.
The materials are reseparated at each successive ridge or bump.
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The invention will now be further described by way of
example with reverence to the accompanying drawings in which:
use 1 it a part section through one embodiment of a magnetic
EJeparator in accordance with -the invention showing one form of
diversiorl mean and
ire 2 it a diagram illustrating alternative forms of
diversion means.
Referring to Figure 1 of the drawings the separator
comprises linear dipole superconducting cryogenic magnet generally
indicated at 10 and a flat substantially rectangular cross section
separation channel formed between a wall 16 of the magnet and
an outer wall 15.
The material to be separated is fed from a hopper 20
through an adjustable choke feed to fall adjacent the wall 16 of
-the magnet in a stream about 10 mm thick.
to magnetic force is adjusted, depending on the ore
to be separated so that the ore 22 falls down the side of the
magnet under the influence of gravity, the magnetic portion of the
ore being drawn towards the magnet and held against the wall.
This tends to reduce the falling velocity and increase the residence
time for separation. A smooth bump 24 (or its equivalent) is provided
on the wall 16 extending across the width of the channel wall, which
causes the ore falling against or adjacent the wall and especially
the non-magnetic fraction, to be diverted horizontally away from the wall
to increase the physical dispersion of the magnetic and non-magnetic
fractions
Substantially non-magnetic mineral is diverted away from the magnetic
mineral which tends to be retracted by the magnet back towards the
wall 16.
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finally the relatively magnetic material falls adjacent the magnet
and the relatively non-magnetic material away from the magnet, the
two streams M and NM being separated by an adjustable flat splitter
member 26 whose position can readily be adjusted towards or away
from the flat wall lo.
o feed the mineral into the channel a simple linear
choke feed is required.
he feed channel can, if desired, be divided into a
horizontal series of thin vertical channels, e.g. each 30 mums
deep, each receiving a stream of crushed ore to be separated,
instead of one broad channel, given that the magnetic field is
of sufficient extent (say 100 mm) to encompass all the channels.
or example, if a second channel is used on both sides
this will be positioned outwardly of the channel shown in figure 4,
where the magnetic field is weaker. A first pass of the material
may be made through this second channel and then a final or
second pass through the first channel adjacent the magnet where
the field is stronger.
As an example of the separation achieved tests were
made on phosphate mineral containing about 14% appetite mineral
and analyzing as 5.8% P205. In a separation at a modest
magnetic field of 24,000 gauss at a flow rate of 9 ton our per
moire of magnet length ore was passed over two bumps of 10 mm
projection from the magnet face. the ore had a free fall of
100 mm from the linear hopper during which fall it was held
against the face of the channel adjacent to the magnet by the
magnetic field. below each bump the ore was split into magnetic
and non-magnetic fractions. ale magnetic from the first bump
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were passed over the second bump, the two non-magnetic fractions
were combined for retreatment at a higher field. m e splitter
below each bump was positioned 30 mm away from the magnet face
and 70 lo below the centre of the bump. The non-magnetic product
was of% of the mass. The magnetic product was discarded as
waste mineral. The recovery of appetite was 77% in the non-
magnetic product. this product was then retreated at a higher
field of 31000 gauss.
Again the mineral was passed over two bumps of 10 mm
projection after a 100 mm free fall. the splitter was set at
20 mm from the magnet wall and 70 mm below the bump. The non-
magnetic product from the first bump analyzed at 38.3% P205 or
90.3% phosphate. Magnetic measurement of the susceptibility
indicated 93% phosphate. m e nonmagnetic product from the
15 second bump represented 32.4% P205 or 76% appetite. m e recovery
of this second double stage of separation was owe. The final
product is of sufficient commercial grade.
Referring to Figure 2, aback" ramp having the shape of
either a) or b) may be used instead of the rounded top humps or
bump to cause the particles to be thrown or moved out away from
the magnet during their free fall path.
- The dimensions of the two "scrimps shown in figures
pa and 2b are as follows:
Shape No. a: Length Of 18.9 cm;depth D, 1.25 cm; angle x-= 16~
25 Shape No. b: ~engthCE'15.3 cm; depth D' 1.5 cm; angle x = 161 .
Shape No. b is mainly used for the first or cleaning pays whilst
shape No. a is mainly used for the final separation slop.
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m e "ski" ramp shown in figures pa and 2b illustrate the actual
dimensions of the "ski" ramps used.
Although the applicants are unable to state with
accuracy what the maximum free-fall velocity it a-t which the "ski"
ramp still operate effectively, it may be mentioned that the
aforementioned tests were carried out under conditions where the
ore fell for a distance of approximately 115 mm before it reached
the separation point of the "ski" ramp. With -the aid of a
high-speed camera, it has been determined that the free-fall
velocity of the particles is then 1.5 m/s. At this velocity
acceptable metallurgical results were obtained. Poor metallurgical
results were obtained when ore was allowed to free-fall for a
distance of approximately 1000 mm, reaching a velocity of
approximately 4.5 m/s. It is believed that even poorer
metallurgical results would be obtained at velocities greater
than 4.5 m/s.
