Size recovery curves of minerals in industrial spirals for processing iron oxide ores

• Mineral size recovery curves in spirals are calculated using data from two iron ore processing plants.
• Recovery of iron carrier particles increase up to 0.2 mm and then decreases due to the Bagnold force.
• The decrease of recovery for coarse silica carrier particles is more important than that of iron carrier particles.

Spirals are gravity concentrators used for the concentration of coal, iron oxide ore and heavy minerals. As in any gravity concentrators the separation of minerals in a spiral is based on particle size and specific gravity. The size recovery curves of minerals in mineral processing equipment provide an efficient way to analyse the operation of spiral concentrators. However unlike other gravity concentrator equipment such as hydrocyclones or hydraulic classifiers a drop of recovery in the region of coarse particles is observed for spirals. This decrease of recovery of coarse particles is observed for the valuable and gangue minerals of roughing, cleaning and re-cleaning spirals of two Canadian iron ore concentrators. Any improvement in the recovery of coarse iron carrier particles can lead to a significant increase in the plant revenues.

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