Crushed ore rides a belt into the field of a rotating magnetic drum at the discharge end. Magnetite grains (Fe₃O₄) are attracted to the drum and cling to it past the point where gravity alone would drop them, so they fall into a separate concentrate chute; non-magnetic gangue leaves the belt on its normal ballistic path into the tailings bin. The same closed-form recovery/grade formulas as the 3D lab drive both the physics and the readout:
chance = clamp(0.08 + field·1.03
− max(0, size−3)·0.055
− max(0, feed−45)·0.006, 0.02, 0.98)
recovery% = clamp(34 + field%·0.73
− max(0, size−3)·3.1
− max(0, feed−44)·0.52, 7, 97)
grade% = clamp(49 + field%·0.27
− max(0, 2.5−size)·2.3
− max(0, feed−50)·0.25, 42, 76)
A grain is magnetic with 42% base probability; whether it is actually captured is then a coin flip against chance, so coarse (>3mm) or overloaded (>45t/h) feed visibly lets more magnetite slip into the tailings.
- Field strength — a stronger drum field raises both the per-grain capture chance and the modelled bulk recovery.
- Feed rate — pushing more ore per hour shortens each grain's exposure time to the field, cutting recovery once above ~45 t/h.
- Particle size — coarse grains carry more inertia than the magnetic force can overcome once size exceeds ~3 mm.