Mineral Processing and Extractive Metallurgy
Mineral Processing and Extractive Metallurgy tests the chain from liberation to metal: comminution, sizing, concentration, roasting, smelting, converting, leaching, electrowinning, and refining. Numerical questions often use grade-recovery balances or Faraday's law.
Core rules
- Comminution: Bond's law W=10Wi(1/√P−1/√F), with Wi in kWh/t and sizes in µm; operate near optimum liberation, not maximum fineness.
- Grade-recovery balance on a two-product separator: Recovery R = Cc/(Ff) ×100%; concentrate grade c, feed grade f, tail grade t. With consistent mass units, R = c(f−t)/(f(c−t)).
- Gravity, magnetic, electrostatic, and froth flotation separate by density, susceptibility, conductivity, and surface wettability.
- Roasting is gas-solid oxidation/reduction; calcination removes CO2 or water; smelting reduces and melts; converting oxidizes impurities.
- Hydrometallurgy: leaching selectivity, purification, and electrowinning. Faraday's law: m = MIt/(nF).
Worked example
Feed assays 1.0% Cu, concentrate 25% Cu, tail 0.1% Cu. On 100 g feed, Cu feed =1.0 g. Let concentrate mass = C. Cu balance: 1.0=0.25C+0.001(100−C). Thus 1.0=0.249C+0.1, C=3.614 g. Cu in concentrate=0.25×3.614=0.9035 g. Recovery=0.9035/1.0=90.35%. The high concentrate grade does not guarantee high recovery; both must be reported.
Traps
- Confusing grade (concentration in a stream) with recovery (fraction of feed metal recovered).
- Using different dry-mass bases for feed and products.
- Forgetting the number of electrons n in Faraday's law.
- Treating roasting and calcination as interchangeable.
- Ignoring gangue in smelting mass balances.