Fundamentals of Dry Magnetic Separation for Iron Ore
Dry magnetic separation is a critical mineral processing technique used to concentrate and purify iron ore without the need for water. It is particularly useful in arid regions or where water scarcity is a concern. Below are the key fundamentals:
1. Principle of Dry Magnetic Separation
– Magnetic Attraction: Iron ore particles (e.g., magnetite, hematite) are separated based on their magnetic susceptibility.
– Non-Magnetic Gangue Rejection: Non-magnetic impurities (e.g., silica, alumina) remain unaffected and are removed.
– Dry Processing: Unlike wet magnetic separation, no water or slurries are used, reducing environmental impact.
2. Types of Iron Ore Suitable for Dry Magnetic Separation
– Strongly Magnetic Ores (Magnetite – Fe₃O₄): Easily separated due to high magnetic susceptibility.
– Weakly Magnetic Ores (Hematite – Fe₂O₃): May require high-intensity magnetic separators or pre-treatment (e.g., roasting to convert hematite to magnetite).
3. Key Equipment Used
– Low-Intensity Magnetic Separators (LIMS):
– Used for highly magnetic ores (e.g., magnetite).
– Includes drum separators with permanent magnets or electromagnets.
– High-Intensity Magnetic Separators (HIMS):
– Required for weakly magnetic ores (e.g., hematite).
– Includes induced roll magnetic separators (IRMS) and rare-earth drum separators.
– Rare-Earth Roll Magnetic Separators (RERMS):
– High-gradient separation for fine particles.
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4. Process Steps
1. Crushing & Screening:
– Ore is crushed and screened to optimal size (~0.5–6 mm).
2. Pre-Concentration:
– Low-intensity magnets remove coarse magnetite early in the process.
3. Magnetic Separation:
– Material passes through a magnetic field; iron-rich particles are attracted while gangue is discarded.
4. Product Collection:
– Magnetic concentrate is collected; tailings (non-magnetic waste) are rejected.
5. Advantages of Dry Magnetic Separation
– No water consumption → suitable for dry regions.
– Lower operational costs compared to wet methods.
– Reduced environmental impact (no tailings ponds).
– Simpler setup and maintenance.
6. Challenges
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