Magnetic Separation Process Technology for Ore

1. Pure Magnetite Ore

In pure magnetite ore, the predominant iron mineral is magnetite. This type of ore has the longest history in mineral processing. Due to its simple composition, weak magnetic separation is commonly employed.

For medium to large-scale magnetic separation plants:

- When the grinding size exceeds 0.2 mm, single-stage grinding followed by magnetic separation is typically used. When the grinding size is less than 0.2 mm, two-stage grinding magnetic separation is employed. If coarse grinding can produce qualified tailings, staged grinding magnetic separation is adopted.

In water-scarce regions, dry grinding and dry magnetic separation are used. For depleted magnetite ore or low-grade magnetite ore, dry magnetic separation is generally applied to remove gangue. The former yields lumpy enriched ore; Both are then processed through grinding and magnetic separation to obtain concentrates.

To achieve high-grade concentrates, magnetite concentrates may undergo reverse flotation or impact screening. To enhance recovery rates, processes such as tailings reprocessing may be considered for further recovery.

2. Polymetallic Magnetite Ore

Multimetallic magnetite ores contain silicate or carbonate gangue minerals, often accompanied by pyrite, cobaltite, chalcopyrite, apatite, etc. Extensive beneficiation practices exist for such ores, typically employing a combined weak magnetic separation and flotation process: weak magnetic separation recovers iron, while flotation recovers sulfides or apatite.

The principle flowsheets are divided into two types: weak magnetic separation-flotation and flotation-weak magnetic separation. These two flowsheets differ in the disposition of magnetite-sulfide intergrowths: in the former, intergrowths primarily enter the iron concentrate; in the latter, they mainly enter the sulfide concentrate. Therefore, at the same grinding size, the flotation-first, magnetic-second process yields an iron concentrate with lower sulfide content and a sulfide concentrate with higher recovery rates.

Such ores often exhibit self-fluxing properties, necessitating careful preservation of this characteristic in the concentrate. Some ores also contain elevated magnesium levels, where magnesium may exist as a solid solution within magnetite, making mechanical separation from iron challenging.

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