Mineral Processing: Crushing
Crushing is the first mechanical stage in mineral processing, aimed at reducing the size of mined ore for subsequent liberation and separation of valuable minerals. Here’s a detailed breakdown:
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1. Purpose of Crushing
– Size Reduction: Break large rocks/ore into smaller fragments for easier handling and downstream processing (e.g., grinding, concentration).
– Liberation: Free valuable minerals from gangue (waste rock) by creating particles small enough for separation.
– Optimization: Achieve a size suitable for grinding mills (typically ≤10–20 mm for ball mills).
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2. Stages of Crushing
Crushing is typically done in 2–4 stages, depending on ore hardness and target size:
| Stage | Equipment | Feed Size (Input) | Product Size (Output) |
|————-|——————————-|——————-|———————–|
| Primary | Jaw Crusher, Gyratory Crusher | 1.5 m – 0.5 m | 100–200 mm |
| Secondary| Cone Crusher, Impact Crusher | 200–100 mm | 20–50 mm |
| Tertiary | Cone Crusher, HPGR | 50–20 mm | 5–10 mm |
| Quaternary (if needed) | Vertical Shaft Impactors (VSI) | <20 mm | <5 mm |
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3. Key Crushing Equipment
# (a) Primary Crushers
– Jaw Crushers: Use compressive force; ideal for hard, abrasive ores.
– Gyratory Crushers: Higher capacity than jaw crushers; suited for large-scale operations.
# (b) Secondary/Tertiary Crushers
– Cone Crushers: Provide finer crushing via compression and attrition.
– High-Pressure Grinding Rolls (HPGR): Energy-efficient alternative for hard ores.
– Impact Crushers: Use.jpg)
mmers/blow bars; best for softer ores (e.g., limestone).
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4. Factors Influencing Crushing Performance
– Ore Characteristics: Hardness (Mohs scale), abrasiveness, moisture content.
– Feed Size vs. Product Size: Determines the number of crushing stages required.
– Throughput