Ore Pre-Concentration: Value Before the Mill

Grinding is the most expensive thing a concentrator does. Pre-concentration rejects barren rock before it gets there.

Ore pre-concentration is the rejection of barren waste rock at coarse particle sizes — before grinding — using sensor-based sorting or density separation, so the mill processes only material worth grinding. It typically rejects 30–50% of feed mass, cuts operating cost per tonne of metal by 40% or more, and multiplies feed grade 2–5×.

Why pre-concentrate ore before grinding?

Grades are falling, energy prices are climbing, tailings dams are filling — yet conventional plants still grind every tonne of run-of-mine ore to powder, waste included. Comminution typically consumes ~40% of a concentrator's power.

The full-size-fraction answer

• 60–10 mm → XRT photoelectric sorting. X-ray transmission reads density through each rock; ejectors kick out waste at throughputs of hundreds of t/h, bone dry.
• 10–0.5 mm → dense medium cyclones. Centrifugal separation in a ferrosilicon/magnetite medium at 0.1 m³/t of fully recycled water.
• −0.5 mm → flotation and other processes. Fines proceed to conventional routes — now at a fraction of the original tonnage.

What operators gain

• Operating cost cut ≥40% per tonne of metal
• Feed grade multiplied 2–5× (see our case studies: fluorite ×2, copper ×2.7, spodumene ×4.5)
• Existing mill capacity effectively doubled
• Low-grade and waste-dump resources become economic

Delivery models

Test (1-tonne sample, results in 24 h) → Design → EPC → Operate. Available as EPC, EPC+O&M, or BOT — we will build and run the plant, as we do for a 300,000 t/a fluorite operation in Mongolia under a 10-year contract.

The mass balance, worked

Take 100 t/h of feed at 1.00% metal. Reject 40 t/h of barren rock at 0.10%: the remaining 60 t/h now runs 1.60% — a 1.6× grade lift with 96% recovery before a single kWh of grinding. Comminution energy (typically 15–25 kWh/t) is now spent on 60 t instead of 100, flotation capacity is freed by the same ratio, and tailings storage shrinks by 40%.

What it does to cut-off grade

Because pre-concentration removes cost per tonne of metal, it lowers the economic cut-off grade — ore previously classified as waste re-enters reserves. The same logic applies retroactively to tailings piles and waste dumps: material that was already mined becomes feed again.

Interface engineering

The three windows are not independent machines but one flowsheet: XRT rejection reduces DMC feed tonnage; the DMC's −0.5 mm de-sliming protects flotation from medium contamination; shared water and medium circuits close the loop at 0.1 m³/t. Getting these interfaces right — screen apertures, medium carry-over limits, surge capacity — is where operating experience earns its keep.

Frequently asked questions

Q: Which ores are candidates?
Any ore with a density or atomic-number contrast between value mineral and gangue at coarse liberation: fluorite, spodumene, tungsten, tin, antimony, lead-zinc, copper, phosphate, barite, graphite — plus tailings and low-grade stockpiles. When in doubt, a one-tonne sample answers the question in 24 hours.

Q: How much sample do you need, and what do we get back?
About one tonne of representative ore. You receive washability/sortability curves, the recommended cut point, a full mass balance and a feasibility view — results within 24 hours of sample receipt.

Q: What metal loss should we expect?
Campaign-dependent: our portfolio spans 1.6% (lead-zinc) to 18.8% (coarse oxide copper, deliberately traded for capacity). The cut point is an economic optimization, not a fixed setting — we model it against your power, haulage and downstream costs.

Q: Does this replace our existing plant?
No — it sits in front of it. The mill keeps running; it simply stops grinding barren rock. Existing concentrators typically gain 30–60% effective capacity.