24-MMP-A3 Mineral Processing · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-MMP-A3 Mineral Processing, 2018-May. 3 hours duration, closed book; only an approved Casio or Sharp calculator permitted. Six questions constitute a complete exam paper (100 marks total).
Reference texts: Wills & Finch, Wills' Mineral Processing Technology, 8th ed. (metallurgical balances, recovery/enrichment ratio and separation efficiency – Ch. 1 & 12; comminution, crushers and mills – Ch. 6; gravity concentration – Ch. 10; magnetic and electrostatic separation, heavy-mineral-sand flowsheets – Ch. 13; froth flotation, cells and reagents – Ch. 12; classification, hydrocyclones and partition curves – Ch. 9; solid-liquid separation and tailings dams – Ch. 15 & 17); Taggart, Handbook of Mineral Dressing (heavy-liquid density calculations, classical two-product formulas).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Approach. Zircon (SG 4.7, non-magnetic, non-conductor) must be separated from eleven other minerals using only physical property contrasts – there is no single property that isolates it directly, so the flowsheet stages three physical separations in series, each stripping out the minerals zircon does NOT share a property with, in the standard heavy-mineral-sand processing order (gravity → magnetic → electrostatic): (1) SG separates the dense "heavy mineral" suite from the light silicate gangue; (2) magnetism removes the magnetic/highly-magnetic minerals from the non-magnetic survivors; (3) electrical conductivity splits the remaining non-magnetics into conductors (rejected) and the non-conductor zircon (final concentrate).
Stage 1 (gravity) exploits the largest single contrast in the table: quartz/mica/tourmaline sit at SG 2.6–3.0 while every other listed mineral is SG ≥ 3.4, so a spiral or shaking-table cut at roughly SG 3.2–3.4 cleanly rejects the bulk gangue mass with one stage. Stage 2 (magnetic) is itself staged from weak to strong field intensity: a low-intensity drum first pulls out the highly-magnetic magnetite (which would otherwise foul or coat a high-intensity unit), then a high-intensity (induced-roll or rare-earth-roll) separator removes the remaining magnetic minerals – ilmenite, siderite, garnet, monazite and staurolite – leaving only rutile, pyrite and zircon, all non-magnetic. Stage 3 (electrostatic) is the only property that discriminates within that trio: rutile and pyrite are conductors that lose their induced charge quickly on a grounded rotor and are thrown clear, while zircon is a non-conductor that holds its charge and is pinned to the rotor until mechanically brushed off as the final concentrate.
Check. This is the standard industrial heavy-mineral-sand separation train (gravity → magnetic → electrostatic), and the property table given supports it directly. Real plants also dry and desli me between wet gravity and dry magnetic/electrostatic stages (these units require a dry, sized feed) – that conditioning step is implied here but not drawn as a separate block since the question asks only for the major process steps and rejected minerals at each.
| Stage | Property exploited | Minerals rejected |
|---|---|---|
| 1. Gravity concentration | Specific gravity | Quartz, mica, tourmaline (SG < 3.4) |
| 2a. Low-intensity magnetic | Magnetic susceptibility (strong) | Magnetite |
| 2b. High-intensity magnetic | Magnetic susceptibility (weak/moderate) | Ilmenite, siderite, garnet, monazite, staurolite |
| 3. High-tension electrostatic | Electrical conductivity | Rutile, pyrite (conductors) |
| Final concentrate | — | Zircon (non-magnetic, non-conductor) |
