Magnetic Separation

Report
Lecture 11 – MINE 292
Main Applications
1.
Tramp Metal Removal
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2.
Magnetite Recovery
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3.
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Scheelite, talc, quartz, kaolinite,, industrial minerals
DMS Magnetite Recovery
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6.
Nickel recovery
Gangue removal (zinc ores, gold ores, nickel ores)
Magnetic minerals removal
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5.
Primary iron ore processing (taconite ores)
Pyrrhotite Recovery or Removal
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4.
To protect crushers (electromagnets as well as metal detectors)
Media recovery and upgrading (purification)
Cleaning hematite concentrates (high-intensity)
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Final stage upgrading
Types of Materials
 Diamagnetic
 Repulsion by magnetic forces
 Paramagnetic
 Attraction to magnetic forces
 Rutile, ilmenite, chromite
 Ferro-Magnetic
 Very-highly attracted to magnetic forces
 1,000,000 times effect of paramagnetism
 Effect disappears above Curie temperature (~620 °C)
 Iron, nickel, magnetite, pyrrhotite
Field Strength and Flux Density
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Magnetic Induction (flux) = B in Tesla
Field Intensity induced through particle = H (A/m)
Permeability = µo (T·m/A)
Magnetization Intensity = M (4π x 10-7 T) - ignored
B = µo (H + M)
B = µo H
 For ferromagnetic materials, must consider magnetic
susceptibility (S = M/H)
B = µo H (1 + S)
Magnetization vs. Field Intensity
 Slope = S (magnetic susceptibility)
Magnetization vs. Field Intensity for Fe3O4
 Slope = S (magnetic susceptibility)
 For H = 1 T, S = 0.35
 Full saturation at 1.5 T
 Iron saturates at ~ 2.3 T
Magnetic Field Gradient
 Capacity depends on field gradient as well as field intensity
 Rate at which intensity
increases as surface of
magnet is approached
 F is proportional to
H x dH/dl
 Introduction of magnetic particles has the same effect but
agglomeration of particles will block the separator
Magnetic Induction Required for Different Minerals
Methods
 Low-intensity (LIMS)

600 – 700 gauss (0.6-0.7 Tesla)
 High-intensity (HIMS)
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WHIMS (wet)
10,000 gauss (10 T)
 High-gradient (HGMS)
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Fine magnetic matrix
15,000 gauss (15 T)
 Permanent Rare-Earth Magnetic Separators (PREMS)
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500-1,000 gauss (0.5-1.0 T)
 Super-Conducting Magnetic Separation (SCMS)
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50,000 gauss (50 T)
 Eddy-Current Magnetic Separation (ECMS)
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Application of current to mixture of substances
Separation of metals in electronic waste
CBM (cross-belt magnetic separator)
 Magnets (5-6) located above belt
 Operating variables
 Field strength (up to 15 T)
 Pole gap typically 2 mm
 Belt speed (fixed)
 Splitter position (manually adjusted)
 Feed rate ~1.5 tph
Cross-belt Self-cleaning Separator
IRM (induced roll magnetic separator)
 Operating variables
 Field strength (up to 15 T)
 Pole gap typically 2 mm
 Roll speed (fixed)
 Splitter position (manually adjusted)
 Feed rate ~2.5 tph
Induced Roll - Magnetic Pulley
Suspended Magnets – tramp metal
LIMS Units
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Applied to coarse sized particles that are strongly magnetic
Drum-type separators
Dry for sizes > 0.5 cm
Wet for sizes < 0.5 cm
Called Cobbing
Applied to DMS media recovery and upgrading
Typical field strength = 0.6-0.7 T
Gap for Magnetite = 50-75 mm
Gap for pyrrhotite = 10-15 mm down to 2 mm
uses permanent ceramic or rare-earth magnets
LIMS Units
Drum
Diameter
(mm)
600
900
1200
1500
Cylinder Rotation
Length
Speed
(mm)
(rpm)
1200-1800 35
1800-2400 28-35
1800-3000 18
3000
16
Capacity
(tph)
10-30
40-70
80-180
150-260
Feed
Top Size
(mm)
2
3
3
3
Power
(kW)
1.5-2.2
3.0-4.0
5.5-7.5
11.0
Drum Magnetic Separator
Counter-current Magnetic Separator
Magnetic Separator Stages
High-Intensity Magnetic Separation
 Dry High Gradient Magnetic Separator
WHIMS
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Must remove highly-magnetic material to prevent blocking
Feed size > 1mm
Constant supply of clean, high-pressure water
Steady feed rate and density
Generally applied for fine particle removal
Final stage cleaning or upgrading
Field Strength up to 15 T (electromagnetic)
Feed rate = 25-30 tph for 16-pole unit
Gap typically 2 mm
Splitter position varied to control process
Jones High-intensity Separator
Continuous Carousel Mag Sep
Superconducting Cryogenic Mag Sep
Eddy-Current Magnetic Separation
 Applied in recycling industry
 Diamagnetic materials can be separated
 Spinning magnets cause an eddy-current in Aluminum such
that a magnetic field is created that repels Al particles
Grades of DMS Media
CARPCO EDS Lab Unit
CARPCO high-tension separator
Mineral Behaviour in EDS
Multi-stage EDS in practice
Beach Sand Processing for R-E and Zr
Beach Sand Processing for Zircon
EDS at Wabush Scully Mine
EDS applied to copper wire/glass/PVC
Automatic Sorting
 Sensors
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Cameras & Video cameras
X-ray tubes
lasers
 Types
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Photometric - colour/reflectance optical properties
Radiometric - gamma radiation - Uranium
UV - scheelite
Conductivity - sulfides
Magnetic - iron minerals
X-rays luminescence- diamonds
microwave attenuation
hyper-spectral
neutron absorption - boron
Electronic Sorting
Principles of Photometric Sorting
End of Lecture

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