Innovations in Tungsten Preconcentration: From Dense Media to X-Ray Sorting

1. Necessity of Preconcentration

Depleting high-grade resources and increasing low-grade ore ratios (e.g., scheelite <0.4% WO₃) necessitate preconcentration. With up to 90% waste rock dilution during mining, discarding >30% gangue upfront reduces grinding costs, energy consumption, and environmental impact.

2. Key Preconcentration Technologies

1.    Manual Sorting

o    Principle: Surface features (color/texture) differentiation.

o    Method: Handpicking for 18–200 mm particles.

o    Advantages: 40%–60% gangue discard rate.

o    Limitations: Low efficiency, high labor intensity.

2.    Gravity Separation

o    Principle: Density differences (wolframite: 7.2–7.5 g/cm³; scheelite: 5.8–6.2 g/cm³).

o    Methods:

§  Dense Media Separation (DMS): Cyclones/drum separators (density: 2.37–2.7 g/cm³) for -15+0.5 mm ore; 43%–62% discard rate, 5%–8.5% WO₃ loss.

§  Jigging: Movable-sieve jigs for -12+1 mm ore; >50% discard rate, >90% recovery.

§  Spiral Concentrators/Chutes: Low-water consumption; 31%–37% discard rate.

§  Centrifugal Separation: For slimes (<0.5 mm); 82%–86% WO₃ recovery.

3.    Magnetic Separation

o    Principle: Magnetic properties (e.g., wolframite’s weak magnetism).

o    Method: Low-intensity magnet for iron removal → high-intensity magnet for tungsten; or pre-discarding before flotation.

o    Performance: 48%–86% discard rate, concentrate WO₃ grade up to 0.34%–4.27%.

o    Limitation: Only for ores with significant magnetic contrast.

4.    Intelligent Sensor-Based Sorting

o    Principles:

§  Image Color Sorting: High-res cameras detect surface differences; 72%–85% discard rate for wolframite.

§  XRT Sorting: X-ray penetration analyzes density/composition; handles -80+15 mm ore; 75%–92% discard rate, <0.017% WO₃ loss.

o    Advantages: >99% accuracy, automation, replacing manual sorting.

3. Selection Criteria & Trends

·         Ore Type: Image sorting/magnetic separation for wolframite; gravity/XRT for scheelite.

·         Particle Size:

o    Coarse (>15 mm): DMS/XRT/manual

o    Medium-fine (-15+0.5 mm): Jigging/spirals

o    Slimes (<0.5 mm): Centrifugal concentrators

·         Future Focus: Intelligent systems (XRT, AI) with enhanced adaptability.