Mineral processing plants use various types of mills to grind and reduce the size of ore particles, liberate valuable minerals from gangue, and prepare the material for subsequent separation processes. Here are the main types of mills commonly used:
1. Tumbling Mills (Rotary Mills)
– Ball Mill: Uses steel balls as grinding media to crush and grind ore. Suitable for both wet and dry grinding.
– Rod Mill: Uses long steel rods instead of balls, ideal for coarse grinding and minimizing overgrinding.
– Autogenous (AG) Mill: Uses the ore itself as grinding media (self-grinding). No or minimal steel balls/rods.
– Semi-Autogenous (SAG) Mill: A combination of AG milling with a small percentage of steel balls to assist grinding.
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2. Stirred Mills (Vertical Mills)
– Stirred Media Detritor (SMD): High-energy vertical mill using fine grinding media for ultrafine grinding.
– Vertimill®: Energy-efficient stirred mill for fine and regrind applications.
– IsaMill™: High-speed horizontal stirred mill for ultrafine grinding (<10 µm).
3. Impact & Hammer Mills
– Hammer Mill: Uses rapidly rotating hammers to crush ore; common in secondary crushing.
– Pin Mill / Disc Mill: Uses impact between rotating discs or pins for fine grinding.
4. Roller Mills
– High-Pressure Grinding Rolls (HPGR): Compresses ore between two counter-rotating rollers, reducing energy consumption compared to ball mills.
– Vertical Roller Mill (VRM): Used for grinding coal, cement, and minerals.
5. Specialized Mills
– Jet Mill / Fluid Energy Mill: Uses high-speed gas jets to achieve ultrafine particle sizes via particle collisions.
– Vibratory Mill: Uses vibration to enhance grinding efficiency in small-scale applications.
– Attrition Mill: Grinds material between rotating discs with abrasion action.
Selection Factors:
– Feed size & desired product fineness
– Ore hardness & abrasiveness
– Wet vs. dry processing
– Energy efficiency & cost
– Downstream processing requirements
Each mill type has advantages depending on the mineral type and processing stage (primary crushing, secondary grinding, or ultrafine regrinding). Would you like details on a specific mill type