Jan Svoboda. Magnetic Techniques for the Treatment of Materials
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100 CHAPTER 2. REVIEW OF MAGNETIC SEPARATORS
Table 2.4: Various models of Jones WHIMS.
Type Capacity [t/h] Mass [t] Rotor diameter [m]
DP 335 180 114 3.35
DP 317 120 98 3.17
DP 250 75 70 2.50
DP 140 25 30 1.4
DP 90 10 16 0.9
Figure 2.39: Jones WHIMS DP 317 (courtesy of Humboldt Wedag AG).
achieved with the matrix installed in the plate box. The Jones separators are
available in several sizes, some of them are summarized in Table 2.4. A photo-
graph of a DP 317 separator is shown in Fig. 2.39.
The Jones magnetic separators have been widely used in the mining industry
to beneficiate a wide spectrum of minerals. Although these separators have been
used to upgrade industrial minerals such as glass sand, feldspar and bauxite,
the main area of application has been the concentration of weakly magnetic
iron ores. The success of Jones separators has been based on sound mechanical
design and reasonably e!cient performance. However, the grooved plates have
proved to be an obstacle to long-term trouble free operation. As a result of
the high filling factor of the matrix, several problems have been experienced.
The frequently blocked matrix has to be removed from the plate boxes and the
hard sediment must be laboriously removed. Also the eort to flush the matrix,
2.4. WET HIGH-INTENSITY MAGNETIC SEPARATORS 101
Figure 2.40: Schematic diagram of the three-stage 6-ERM-35/135 magnetic sep-
arator [U2].
which represents up to 80 % of the volume of the plate boxes, with high-pressure
water, sometimes results in uncontrolled spillage.
6-ERM-35/135 high-intensity magnetic separator
The 6-ERM-35/135 WHIMS was developed in the former USSR in order to
meet the increasingly demanding requirements for beneficiation of complex ox-
idized iron ores. It was observed [U2] that Jones separators could not ensure
the e!cient separation of ores with complicated mineral composition and fine
dissemination, such as the deposits of Krivoy Rog and Kursk Magnetic Anom-
aly. While the design of the ERM separator is based on the Jones concepts,
improved design of the matrix and of the feed mode, and incorporation of sev-
eral stages of separation in one unit resulted in a greater resistance to matrix
blockage, higher recovery and better selectivity of separation [U2, U3, T2].
A schematic diagram of the 6-ERM-35/135 separator is shown in Fig. 2.40.
The three-rotor separator has two electromagnetic systems 1, each consisting
of a magnetic circuit 2, two blocks of coils 3 and an additional upper pole 4.
The rotor blocks 5, shown in Fig. 2.41, are positioned between the poles of
the magnetic system. The upper rotor operates as a scalping stage to remove
magnetite at a magnetic induction of 0.3 T. The lower rotors recover feebly
magnetic particles at increasing magnetic induction, the lowest stage operating
at a magnetic induction of 1.3 T. The throughput is specified as 100 t/h [U2].
The ERM separators are manufactured in the Ukraine by Magnis Co., Lugansk.
102 CHAPTER 2. REVIEW OF MAGNETIC SEPARATORS
Figure 2.41: A rotor of the 6-ERM-35 magnetic separator.
Eriez high-intensity magnetic separator
Various designs of the magnetic circuits, diering from that of the Jones sep-
arators, were employed by other manufacturers of magnetic separators. For
example, in the Eriez WHIMS, the carousel containing the matrix rotates be-
tween two poles of the electromagnet, as shown in Fig. 2.42. The background
magnetic induction of up to 1.2 T in the air gap is generated by oil-cooled coils.
Matrix types commonly used include expanded metal and steel balls. Commer-
cial models range in capacity from 1 t/h to 120 t/h while the required input
power ranges from 3 kW to 360 kW.
A similar design was used by Boxmag-Rapid in their HIW separators. The
matrix in these separators was trapezoidal wire bars placed at an angle in
the carousel. For treatment of particles smaller than 30 m, the wedge wire
was placed horizontally to increase the residence time. Figure 2.43 illustrates a
single-head unit, while a photograph of two single rotor Boxmag-Rapid WHIMS
operating in an ilmenite recovery plant is shown in Fig. 2.44..
Reading wet high-intensity separators
The Reading wet high-intensity magnetic separators are based on yet another
concept of the magnetic circuit design. The magnetic poles of the electromag-
netic system, shown in Fig. 2.45 are arranged along the circumference of the
carousel with polarity illustrated in Fig. 2.46. The iron cores are magnetized
by oil-cooled coils. Each two poles with opposite polarity form a unit in which
a high magnetic field is generated and in which separation is taking place. The
2.4. WET HIGH-INTENSITY MAGNETIC SEPARATORS 103
Figure 2.42: Two-head Eriez CF-600 WHIMS, with capacity up to 60 t/h (cour-
tesy of Eriez Magnetics, Inc.).
Figure 2.43: A single-head Boxmag-Rapid WHIMS (courtesy of Boxmag-Rapid,
Ltd.).
104 CHAPTER 2. REVIEW OF MAGNETIC SEPARATORS
Figure 2.44: Two Boxmag-Rapid WHIMS machines installed in an ilmenite re-
covery plant.
Figure 2.45: A detailed view of the magnet poles in the separation zones of the
Reading WHIMS.
2.4. WET HIGH-INTENSITY MAGNETIC SEPARATORS 105
Figure 2.46: Schematic diagram of operation of the Reading wet high-intensity
magnetic separator (courtesy of Roche Mining).
feed points are located close to the regions of the high magnetic field. While
the non-magnetic fraction passes through the matrix unaected, the magnetic
fraction is flushed from the matrix at the zero field points that occur between
the poles of like polarity.
Grooved plates of the salient type are used as the matrix, with an air gap of
2.5 mm. The radial length of the matrix is 68 mm although a wider version with
120 mm radial length is also available. The throughput of these two versions is
2 t/h to 3 t/h per feed point for the narrower version and 4 t/h to 5 t/h per
feed point for the wider model. The Reading WHIMS, shown in Fig. 2.47, are
manufactured in several models, namely 4 pole (2 feed points), 8 pole (4 feed
points) and 16 pole (8 feed points).
The Reading wet high-intensity magnetic separators were developed by Read-
ing of Lismore (Pty.) Ltd., Australia. They are well established in beach sand
operations. Concentration of ilmenite, chromite and monazite are typical appli-
cations. The units are also applied to the beneficiation of fine weakly magnetic
iron ores and to purification of various industrial minerals such as glass sand.
Figure 2.48 illustrates the assembly of Reading WHIMS for application in the
beach sand industry. The Reading product range was acquired by Roche Mining
MT (formerly MD Mineral Technologies) in 2000.
106 CHAPTER 2. REVIEW OF MAGNETIC SEPARATORS
Figure 2.47: The Reading 16-pole WHIMS (courtesy of Roche Mining).
Figure 2.48: Assembly of banks of Reading WHIMS.
2.4. WET HIGH-INTENSITY MAGNETIC SEPARATORS 107
Figure 2.49: Schematic diagram of the Ferrous Wheel magnetic separator, oper-
ating in rougher/cleaner mode (courtesy of Eriez Magnetics, Inc.).
Ferrous Wheel magnetic separator
A Ferrous Wheel separator combines the basic concept of a high-gradient mag-
netic separator with the low-cost permanent magnet circuit. The principles of
design and operation can be seen in Fig. 2.49. The vertical separating ring con-
sists of two discs with the matrix situated in pockets between them, as shown in
Fig. 2.50. The rings are assembled into a horizontal drum, the length of which is
5.5 m and outer diameter 2.4 m. Rotational speed of the drum is approximately
2rpm.
The length of the matrix, fabricated from screen cloth, is 150 mm. The
choice of the mesh size of the screen cloth is determined by the size distribution
of the feed ore. The separating ring is open in the middle to allow the removal
of the separated products. Barium ferrite permanent magnets are mounted on
each side of the separating rings, as is shown in Fig. 2.51. Each of the two
magnetic heads covers an arc of 60
0
and the magnetic induction generated in
108 CHAPTER 2. REVIEW OF MAGNETIC SEPARATORS
Figure 2.50: The Ferrous Wheel separating ring with 125 mm wide matrix (cour-
tesy of Eriez Magnetics, Inc.).
the gap is 0.1 T.
The Ferrous Wheel separator allows a two-stage separation. The separator
can be configured as either rougher/scavenger or rougher/cleaner, the latter
mode being illustrated in Fig. 2.49. The feed enters the matrix in the magnetic
zone located at the top of the ring. The non-magnetic particles pass through
the matrix and are channeled out of the separator. This fraction represents the
rougher tailings. The magnetic particles, collected onto the matrix, are flushed
from the matrix outside the magnetic field and then introduced, from inside the
separating ring, into the second magnetic head, to remove the entrained gangue
material. An assembly of Ferrous Wheel separators is shown in Fig. 2.52.
Roll-type wet high-intensity magnetic separator
A useful wet alternative to dry induced roll high-intensity magnetic separators
was developed in the nineteen sixties in the former USSR [D4, K2]. These
separators, suitable for treatment of weakly magnetic, relatively coarse materials
(up to 10 mm), consist of profiled rolls that rotate against profiled stationary
poles. The poles and the rolls are magnetized by electromagnetic coils wound
around the iron yoke. Various profiles of the rolls and of the pole pieces, as shown
in Fig. 1.46, have been employed, their selection depending upon the required
magnetic force and the application. Triangular teeth facing grooved poles with
cuts were found to be the most e!cient profile [D4]. Magnetic induction as
high as 1.6 T can be achieved in the working zone of the separator. A schematic
2.4. WET HIGH-INTENSITY MAGNETIC SEPARATORS 109
Figure 2.51: Magnetic system of the Ferrous Wheel magnetic separator. Per-
manent magnets are located on each side of the vertical separating
ring (courtesy of Eriez Magnetics, Inc.).
Figure 2.52: Ferrous Wheel separators under construction at Eriez Magnetics
(USA) (courtesy of Eriez Magnetics, Inc.).