JOHN FINLAY MINING中文JOHN FINLAY MINING中文Fifty years of dense-medium mastery, redeployed from coal to hard-rock minerals — precise density cuts at 0.1 m³ of water per tonne, fully recycled.
A dense medium cyclone (DMC) separates minerals by density in a centrifugal field: ore enters a cyclone filled with a ferrosilicon/magnetite suspension tuned to a precise cut density; dense minerals report to the underflow, light gangue to the overflow. Feed size 0.5–50 mm, separation precision Ep typically 0.02–0.05, water 0.1 m³/t fully recycled.
Ore enters a cyclone filled with a ferrosilicon/magnetite suspension tuned to a precise cut density. In the centrifugal field, dense mineral reports to the underflow, light gangue floats to the overflow. The medium runs in closed circuit; water consumption is 0.1 m³/t, fully recirculated.
Our test campaigns span fluorite (42→84.7%), spodumene (0.91→4.08% Li₂O), high-slime copper, lead-zinc (98%+ recovery), tungsten fines and phosphate.
The John Finlay group has designed and operated dense-medium plants since 1974 — 110+ plants designed by our Shanxi institute, 100+ under trusteeship operation. That operating experience is what we bring to non-ferrous pre-concentration.
| Parameter | Value |
|---|---|
| Feed size | 0.5–50 mm (pressurized two-product systems) |
| Separation density | adjustable ≈1.3–3.2 g/cm³ with FeSi/magnetite blends |
| Separation precision | Ep (écart probable) typically 0.02–0.05 — far sharper than jigs or spirals |
| Density control | nuclear/in-line density gauge, automatic water & medium make-up |
| Medium recovery | sieve bends → drain-and-rinse screens → wet drum magnetic separators → densifier |
| Process water | 0.1 m³/t, fully recirculated; no process discharge |
| Fines interface | −0.5 mm de-slimed ahead of the cyclone, routed to flotation |
A correct-medium sump feeds the cyclone at constant head or pump pressure. Overflow (floats) and underflow (sinks) each pass a sieve bend and a drain-and-rinse screen: the drained medium returns directly to the sump, while rinse water carrying diluted medium passes wet-drum magnetic separators — recovering the ferrosilicon/magnetite for densification and return. A density transmitter on the correct-medium line trims water and thickened-medium addition continuously, holding the cut point within ±0.005 g/cm³ in a well-run plant.
In the cyclone's centrifugal field (up to ~200 g at the apex), near-density particles get repeated chances to report to the correct product — that is what drives Ep down versus water-based gravity devices, and why recoveries in our campaigns hold above 95% even at coarse rejection rates of 40–50%.
Q: What does the medium cost to run?
Ferrosilicon/magnetite losses are the main operating consumable, controlled by drain-and-rinse screen performance and magnetic-separator efficiency. We guarantee medium consumption contractually in O&M projects; site-specific figures come out of the one-tonne test.
Q: How is this different from a jig or spiral?
Sharpness. A DMC separates at an engineered density with Ep typically 0.02–0.05; water-based gravity devices smear the cut across a wide density band, losing near-density value minerals. That sharpness is what lets our campaigns hold 95%+ recovery at 40–50% rejection.
Q: Is 0.1 m³/t of water really the total?
Yes — as make-up for a fully recirculated circuit. There is no process discharge; coarse rejects leave the plant drained and stackable.
Send ~1 tonne of representative ore — washability results within 24 hours of sample receipt.
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