Lecture 11 – MINE 292. Main Applications 1. Tramp Metal Removal To protect crushers (electromagnets as well as metal detectors) 2. Magnetite Recovery.

Magnetic Separation(EDS and Automatic Sorting)

Lecture 11 – MINE 292

Main Applications1. Tramp Metal Removal

To protect crushers (electromagnets as well as metal detectors)

2. Magnetite Recovery Primary iron ore processing (taconite ores)

3. Pyrrhotite Recovery or Removal Nickel recovery Gangue removal (zinc ores, gold ores, nickel ores)

4. Magnetic minerals removal Scheelite, talc, quartz, kaolinite,, industrial minerals

5. DMS Magnetite Recovery Media recovery and upgrading (purification)

6. Cleaning hematite concentrates (high-intensity) Final stage upgrading

Types of MaterialsDiamagnetic

Repulsion by magnetic forces

ParamagneticAttraction to magnetic forcesRutile, ilmenite, chromite

Ferro-MagneticVery-highly attracted to magnetic forces1,000,000 times effect of paramagnetismEffect disappears above Curie temperature (~620 °C)Iron, nickel, magnetite, pyrrhotite

Field Strength and Flux DensityMagnetic Induction (flux) = B in TeslaField 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 IntensitySlope = 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 GradientCapacity 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

MethodsLow-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 beltOperating variables

Field strength (up to 15 T)Pole gap typically 2 mmBelt 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 mmRoll 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 UnitsDrum Cylinder Rotation Capacity Feed PowerDiameter Length Speed Top Size(mm) (mm) (rpm) (tph) (mm) (kW) 600 1200-1800 35 10-30 2 1.5-2.2 900 1800-2400 28-35 40-70 3 3.0-4.01200 1800-3000 18 80-180 3 5.5-7.51500 3000 16 150-260 3 11.0

Drum Magnetic Separator

Counter-current Magnetic Separator

Magnetic Separator Stages

High-Intensity Magnetic SeparationDry High Gradient Magnetic Separator

WHIMSMust remove highly-magnetic material to prevent blockingFeed size > 1mmConstant supply of clean, high-pressure waterSteady feed rate and densityGenerally applied for fine particle removalFinal stage cleaning or upgradingField Strength up to 15 T (electromagnetic)Feed rate = 25-30 tph for 16-pole unitGap typically 2 mmSplitter position varied to control process

Jones High-intensity Separator

Continuous Carousel Mag Sep

Superconducting Cryogenic Mag Sep

Eddy-Current Magnetic SeparationApplied 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 SortingSensors

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

Throughput

25 tph for -25 + 5 mm (1 in to 0.2 in) 300 tph for -300+80 mm (12 in to 32 in)

> 1-2 inches in size with all fines scalped

Reject a portion of feed to reduce comminution costs and possibly produce a very high-grade product.

Talc, magnesite, limestone, phosphates, diamonds, kaolinite, unranium, Pb/Zn, gold ores, glass sands, industrial minerals,

Electronic Sorting

Principles of Photometric Sorting

End of Lecture