Following years of test work in the ferrochrome sector, Multotec said it has successfully developed and proven a spiral concentrator that eliminates beaching and enhances recoveries in the 1- to 3-mm fractions of high-density material. Significantly, when compared to traditional spirals the new spiral has shown extraordinarily higher metal recoveries, even for minus 1-mm fractions in ferrochrome slag, according to the company.

“Our SC25 spiral concentrator features steeper angles which facilitate the flow of material and increase separation efficiency,” said Hlayisi Baloyi, applications engineer at Multotec. “It also widens the particle size range that can be treated by the spiral.

Traditionally, spirals would struggle to efficiently treat material above one millimeter in heavy mineral applications, but this spiral can go well beyond that. The spiral has been a game changer even for the minus one-millimeter size range where higher separation efficiencies have been achieved on chromite ore.”

Baloyi said that this innovation provides an interesting alternative to jigs in the minus 3 to plus 1 size range, which have been one of the conventional methods of separating larger particles. The company said the solution is cost effective as spirals use no electricity and are also easy to maintain. The first order for the commercialized version has been placed.

Multotec claims the economic benefits of the Multotec SC25 spiral for ferrochrome producers are substantial, as some plants were losing the value of their 1- to 3-mm material to tailings. Many of those who used jigs to treat this fraction were also finding that their efficiencies were low.

“Ferrochrome is not the only commodity that we have successfully tested,” said Refentse Molehe, process engineer at Multotec. “We have even seen improved recovery in heavy minerals below one-millimeter size, alluvial chrome, manganese slag and there is potential in industrial recycling.”

Multotec said the recycling application opens up options for urban mining – recovery of metal particles from associated waste. Multotec said it has received a number of requests and conducted tests to recover metals from recycled electronic goods and from customers who intend to recover metal from industrial scrap.