I. Fundamental Principles of Gravity Separation
Gravity separators exploit differences in specific gravity (SG) between minerals to achieve concentration. With gold’s high SG (19.3 vs. 2.7-3.5 for common gangue), this method effectively recovers gold particles through:
- Stratification: Heavier minerals settle faster under pulsating water (e.g., jigs)
- Film separation: Laminar flow carries lighter particles (e.g., shaking tables)
- Centrifugal acceleration: Enhanced G-force traps dense materials (e.g., centrifugal concentrators)
Key Equipment:
- Shaking tables (e.g., 6S-4500)
- Jig separators (JT series)
- Centrifugal concentrators (STLB series)
- Sluice boxes
II. Gold Occurrence & Processing Strategies
1. Rock Gold (Primary Deposits)
- Characteristics: Gold locked in quartz veins or sulfide ores
- Processing Flow:
Crushing → Grinding → Gravity Concentration → Smelting
- Stage 1: Jaw crusher (≤500mm → ≤150mm)
- Stage 2: Ball mill + spiral classifier (≤0.074mm)
- Stage 3: Shaking table for final concentration
2. Placer Gold (Alluvial Deposits)
Types:
- Clay-bound: Requires scrubbing (rotary scrubber)
- Free-milling: Direct screening
Processing Flow:
Washing → Screening → Primary Concentration → Refining
- Coarse gold (>3mm): Jig separator
- Fine gold (0.1-3mm): Centrifugal concentrator
- Ultrafine gold (<0.1mm): Shaking table
III. Optimized Process Design by Scale
Small-Scale Operations (1-2 t/h)
| Feed Size | Recommended Flow | Key Equipment |
| 0-30mm | Direct grinding → Concentration | Wet pan mill + Shaking table |
| 0-130mm | Two-stage crushing → Concentration | Jaw crusher + Hammer crusher + Dual shaking tables |
Medium/Large-Scale Operations (>2 t/h)
| Feed Size | Process Design | Equipment Configuration |
| ≤500mm | Three-stage crushing → Grinding → Classification | Jaw crusher (primary) → Cone crusher (secondary) → Ball mill + Spiral classifier |
| >500mm | Pre-screening → Multi-stage crushing | Grizzly screen → Two-stage jaw crushers → Roll crusher |
IV. Why Choose Gravity Separation?
Technical Advantages
- Zero Chemical Usage:
- Eliminates toxic reagents (vs. cyanidation/flotation)
- Complies with ISO 14001 environmental standards
- Energy Efficiency:
- Power consumption: 1.2-2.5 kW·h/t (vs. 8-15 kW·h/t for flotation)
- Operational Simplicity:
- Minimal training required (startup time <4 hours)
- Maintenance costs: $0.8-1.5/t (60% lower than CIP plants)
Economic Benefits
- ROI: 8-14 months for 50t/d operations
- Recovery Rates
- Placer gold: 85-92%
- Lode gold: 70-78%
V. Equipment Selection Guide
| Gold Type | Particle Size | Optimal Equipment |
| Nuggets | >5mm | Sluice box + Jig |
| Granular | 0.5-5mm | Centrifugal concentrator |
| Flour | <0.5mm | Shaking table |
Pro Tip: Combine centrifugal concentrators (primary) with shaking tables (cleaning) for <0.1mm gold recovery.
VI. Environmental & Safety Considerations
- Water Recycling: Closed-circuit systems reduce consumption to 1.5m³/t
- Dust Control: Wet processing + spray systems maintain PM2.5 <15μg/m³
- Noise Reduction: Rubber-lined equipment lowers noise to <75dB(A)
Technical Validation:
Data sourced from China National Gold Group’s 2023 technical reports and ISO-certified testing centers.
