Magnetic Separation
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Transcript Magnetic Separation
Lecture 11 – MINE 292
Main Applications
1.
Tramp Metal Removal
2.
Magnetite Recovery
3.
Scheelite, talc, quartz, kaolinite,, industrial minerals
DMS Magnetite Recovery
6.
Nickel recovery
Gangue removal (zinc ores, gold ores, nickel ores)
Magnetic minerals removal
5.
Primary iron ore processing (taconite ores)
Pyrrhotite Recovery or Removal
4.
To protect crushers (electromagnets as well as metal detectors)
Media recovery and upgrading (purification)
Cleaning hematite concentrates (high-intensity)
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
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)
WHIMS (wet)
10,000 gauss (10 T)
High-gradient (HGMS)
Fine magnetic matrix
15,000 gauss (15 T)
Permanent Rare-Earth Magnetic Separators (PREMS)
500-1,000 gauss (0.5-1.0 T)
Super-Conducting Magnetic Separation (SCMS)
50,000 gauss (50 T)
Eddy-Current Magnetic Separation (ECMS)
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
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
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
Cameras & Video cameras
X-ray tubes
lasers
Types
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