For Small & Medium Overseas Gold Mines | Alluvial + Lode Gold Combined Gravity Recovery
Many African, South American and Southeast Asian gold mining sites have mixed ore conditions: surface alluvial placer gold deposits alongside outcrop hard rock gold veins. Traditional single-process plants can only run one ore type, leaving lots of gold value locked up. This dual-circuit gravity separation layout solves exactly this pain point. It uses one shared recovery system to process placer gold and crushed hard rock gold at the same time, with low chemical consumption, easy operation and flexible capacity adjustment.
Overview of This Dual Gold Processing Workflow
The whole system starts with a trommel screen for classification. Material below 3mm enters the placer gold recovery circuit directly. Oversized rock >3mm feeds into crushing and grinding circuit for hard rock gold liberation. Both streams finally go through centrifugal concentrator and shaking table for final concentration.
Circuit 1: Placer Gold Recovery Route (< 3mm fraction)
- Trommel Screen: Raw alluvial ore is washed and screened. Clay balls, gravel and fine gold sand are separated. Fine fraction less than 3mm is sent to sluice box; oversize >3mm goes to jaw crusher.
- Sluice Box: Primary roughing gravity separation. Coarse and medium gold grains are trapped inside the sluice mat. It works as a low-cost pre-concentration step to cut down later processing load.
- Centrifugal Concentrator: High-G centrifugal force captures fine free gold that sluice boxes often miss. This is the core equipment to boost fine placer gold recovery rate.
- Shaking Table: Upgrading stage. Centrifuge concentrate is fed onto shaking table to separate high-grade gold concentrate from heavy mineral gangue. Light tailings are discharged.
Circuit 2: Hard Rock Gold Recovery Route (> 3mm rock)
- Jaw Crusher: Primary crushing for hard rock gold ore, breaking big rock into small fragments suitable for ball mill feeding.
- Ball Mill: Wet grinding to liberate gold grains locked inside quartz and sulfide rock. Proper grinding fineness is critical — under-grinding means gold still encapsulated; over-grinding causes sliming and gold loss.
- Centrifugal Concentrator: Recover free liberated gold from ball mill discharge before final table upgrading.
- Shaking Table: Clean and upgrade the centrifugal concentrate to get saleable high-grade gold concentrate. Tailings are discharged separately.
Key Equipment Function Table
| Equipment | Core Function | Best Suitable Ore |
|---|---|---|
| Trommel Screen | Washing, desliming and size classification | Clayey alluvial / placer gold |
| Sluice Box | Low-cost rough capture of coarse gold | Coarse placer gold particles |
| Jaw Crusher | Primary crushing of hard rock ore | Quartz hard rock gold |
| Ball Mill | Wet grinding for gold liberation | Gold-bearing hard rock |
| Centrifugal Concentrator | High recovery of fine free gold | Fine placer & liberated rock gold |
| Shaking Table | High-grade concentrate upgrading | Gravity gold concentrate cleaning |
Why This Dual Circuit Design Works For Small Overseas Mines
- Flexible feed: Switch between placer ore and hard rock ore without rebuilding the whole plant, perfect for deposits with mixed alluvial and lode gold.
- Low operating cost: Pure gravity separation, no cyanide required for free gold, reduces reagent cost and environmental compliance risk.
- High fine gold capture: Sluice + centrifuge + shaking table staged recovery covers coarse, medium and fine gold fractions.
- Modular layout: Can be built in stages. Mine owners can start with placer circuit first, then add crusher & ball mill later when hard rock ore is developed.
- Easy maintenance: These are mature gravity devices, spare parts are easy to source locally in Africa.
FAQ
Q1: What recovery rate can we expect from this gravity line?
A: For free-milling placer gold, total gravity recovery can reach 85%–92%. For free hard rock gold after full liberation, typical recovery is 80%–88%. If gold is locked in sulfides, heap leaching or CIL will be needed as an add-on circuit.
Q2: Can this plant run placer gold and hard rock gold at the same time?
A: Yes. The trommel screen splits feed automatically. Fine sand goes to placer circuit, rock fraction goes to crushing & grinding circuit. Two circuits share the centrifuge and shaking table upgrading section.
Q3: What water and power requirements should we prepare?
A: Gravity separation is water-based. You need stable water supply. For remote sites without grid power, diesel generator sets can be matched to support the whole line.
Q4: Is this flow suitable for high-clay alluvial gold?
A: Yes. The trommel screen has strong washing and scrubbing ability to break clay balls before classification, which avoids clay coating gold particles and lowering recovery.
Need Custom Flow & Capacity Calculation?
Every gold deposit has unique ore properties. Send us your ore sample test report, target TPH, local power and water conditions. Our mineral processing engineers can adjust equipment configuration, sizing and layout for your project.
