The beneficiation of low-grade iron ore involves processes to increase the iron content and reduce impurities (gangue minerals like silica, alumina, and phosphorus) to make it suitable for steel production. Here’s an overview of common techniques:
1. Crushing & Screening
– Low-grade iron ore is first crushed and screened to remove oversized waste rock.
– Jaw crushers, cone crushers, and vibrating screens are commonly used.
2. Grinding (Liberation of Iron Minerals)
– The ore is ground to liberate iron-bearing minerals (hematite, magnetite) from gangue.
– Ball mills, rod mills, or autogenous grinding (AG/SAG mills) are employed.
3. Beneficiation Techniques
Depending on the ore type (hematite/magnetite) and impurities, different methods are applied:
.jpg)
# a) Gravity Separation
– Used for coarse-grained ores with high-density iron minerals.
– Techniques:
– Spiral concentrators
– Jigging machines
– Shaking tables
# b) Magnetic Separation
– Effective for magnetite ores, which are naturally magnetic.
– Low-intensity magnetic separators (LIMS) for magnetite.
– High-intensity magnetic separators (HIMS) for hematite/goethite.
# c) Flotation
– Used for fine-grained ores with silica/alumina impurities.
– Reverse flotation: Silica is floated away from iron using collectors like amines.
– Direct flotation: Iron minerals are floated using anionic/cationic collectors.
# d) Wet High-Intensity Magnetic Separation (WHIMS)
– For weakly magnetic hematite/goethite ores.
– Uses strong magnetic fields to separate iron from gangue.
# e) Selective Hydrometallurgical Processes
– For high-phosphorus or alumi.jpg)
ores:
– Leaching with acids/alkali to remove phosphorus/alumina.
4. Dewatering & Pelletizing/Sintering
– Concentrated slurry is dewatered using thickeners or filters.
– The final product may be pelletized or sintered for blast furnace use.
Challenges in Low-Grade Iron Ore Beneficiation:
✔ High silica/alumina requires advanced separation.
✔ Fine particle sizes need ultra-fine grinding