Magnetic Separation (EDS and Automatic Sorting)

1. Magnetic Separation(EDS and Automatic Sorting) Lecture 11 – MINE 292

2. Main Applications • Tramp Metal Removal • To protect crushers (electromagnets as well as metal detectors) • Magnetite Recovery • Primary iron ore processing (taconite ores) • Pyrrhotite Recovery or Removal • Nickel recovery • Gangue removal (zinc ores, gold ores, nickel ores) • Magnetic minerals removal • Scheelite, talc, quartz, kaolinite,, industrial minerals • DMS Magnetite Recovery • Media recovery and upgrading (purification) • Cleaning hematite concentrates (high-intensity) • Final stage upgrading

3. 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

4. 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 = µoH • For ferromagnetic materials, must consider magnetic susceptibility (S = M/H) B = µoH (1 + S)

5. Magnetization vs. Field Intensity • Slope = S (magnetic susceptibility)

6. 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

7. 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

8. Magnetic Induction Required for Different Minerals

9. 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

10. 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

11. Cross-belt Self-cleaning Separator

12. 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

13. Induced Roll - Magnetic Pulley

14. Suspended Magnets – tramp metal

15. 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

16. LIMS Units Drum Cylinder Rotation Capacity Feed Power Diameter 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 3.0-4.0 1200 1800-3000 18 80-180 3 5.5-7.5 1500 3000 16 150-260 3 11.0

17. Drum Magnetic Separator

18. Counter-current Magnetic Separator

19. Magnetic Separator Stages

20. High-Intensity Magnetic Separation • Dry High Gradient Magnetic Separator

21. 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

22. Jones High-intensity Separator

23. Continuous Carousel Mag Sep

24. Superconducting Cryogenic Mag Sep

25. 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

26. Grades of DMS Media

27. CARPCO EDS Lab Unit

28. CARPCO high-tension separator

29. Mineral Behaviour in EDS

30. Multi-stage EDS in practice

31. Beach Sand Processing for R-E and Zr

32. Beach Sand Processing for Zircon

33. EDS at Wabush Scully Mine

34. EDS applied to copper wire/glass/PVC

35. 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 • 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,

36. Electronic Sorting

37. Principles of Photometric Sorting

38. End of Lecture