Broadening the application of gravity

Gravity concentrators (also commonly referred to as spiral concentrators) are widely applied in the recovery of heavy minerals such as chrome, mineral sands, copper and ferrochrome.

The separation process is based largely on specific gravity with the heavy fraction being separated from the light fraction, a process that occurs as the feed flows down the spiral. In the past, the application of these spirals for heavy minerals was limited to a feed top size of only 1 mm. Any particles larger than this have the tendency of settling the heavy fraction on the spiral trough, which results in poor separation.

New spiral developed

In ferrochrome applications where the feed gets heavier in subsequent cleaning stages, settling on the trough surface happens for particles smaller than 1 mm. Multotec, therefore, developed a new spiral with a top size of 3 mm to specifically treat coarser feeds. This development has advanced the spiral application into the space traditionally dominated by dense media cyclones.

The new spiral presents an additional benefit as it has shown to have high efficiency when treating heavier ferrochrome from slag. 

Multotec SC, HX3 and HX5 Mineral Spiral Concentrators

Multotec’s range of gravity concentrators is one of the most extensive in the world:

Spiral product nameTypical applicationConfiguration
SC20 LG Gold, copper Twin and triple start spirals
SC20 HC Iron ore, chrome High capacity twin start spirals
SC20 VC Mineral sands Twin and triple start spirals
SC21 Chrome, high grade ores Twin and triple start spirals
HX3/HX5 Chrome, iron ore Twin and triple start spirals

Additional benefits to Multotec clients

Multotec offers all of its clients test work on spiral concentrators at its R&D facilities and on-plant, as well as providing consultation services regarding spirals and plants.

Their customers receive design assistance when required and Multotec also offers commissioning of spiral plants and all associated equipment. Yet another Multotec offering for its customers is the company’s spiral plant optimisation services.


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