MechChem Africa March-April 2022

Testing at Multotec improves manganese recoveries Better mineral recoveries are being achieved during test work at Multotec’s in-house testing facility, proving that revenues can be improved and tailings reduced by applying a combination of different technologies. In a recent project for a manganese producer, the company has demonstrated how well its ultra-fine spiral concentrator and magnetic separator work in conjunction.

U sing its extensive in-house testing facility for material from a South African manganese producer, Multotec has defined a solution that will upgrade the quality of saleable concentrate while reducing the content of manganese in tailings. According to Faan Borman, technology manager for research and development in Multotec’s technology division, the customer had specific targets it wanted to reach. These targets aim to optimise revenue from recovered minerals and improve environmental performance, as a level of more than 10% manganese Wet High Intensity Magnetic Separators (WHIMS) from Multotec combine mag- netism, matrix rotation and gravity to paramagnetic materials. Applications include heavy minerals, ilmenite, man- ganese and iron ore (haematite) benefi- ciation; PGM upgrading; as well as man- ganese recovery from slimes dams. This offers innovative new approaches and technology for solving paramagnetic minerals separation processes that are as efficient as they are cost-effective. Magnetic separators that use per- manent magnets can only generate fields of low intensity. These work well in removing ferrous tramp but not fine paramagnet ic part icles. High inten- sity magnetic separators focus on the separation of very fine particles that are paramagnetic. A current is passed through a coil, which creates a magnetic field. This Faan Bornman, Multotec technology manager for Research and Development.

Better recoveries were achieved during test work using the spiral concentrators together with the wet high- intensity magnetic separator (WHIMS) at Multotec’s in-house test facility.

the thickener underflow,” says Borman. “The financial benefit of better recover- ies is to produce a richer concentrate, but it is also to reduce the metal content in tailings – so that it will not be regarded as hazardous waste.” Two sets of test work were des igned and conducted. In the first set, stockpile material with a metal grade of 16% was tested using Multotec’s UX7 ultra-fine spiral concentrator for the roughing and scavenging phases, whi le its SC21 five-turn spiral was used for the cleaning stage. This allowed the target saleable grade of 32% to be achieved, he says, but there was still some work to be done to reach the tailings target grade. “This required some out-of-the-box thinking for the second set of tests, where we ran the material over the wet high- intensity magnetic separator (WHIMS) with a vertical ring,” he says. “At the high- est intensity, this was able to downgrade the spiral tailings material from 13 to 14% right down to 7%manganese – a significant improvement.” He highlighted that for process plants to achieve the most viable solutions they must optimise the use of cost effective equipment and strateg ies . Given the higher cost of applying WHIMS technol- ogy, the testing procedure using spirals

in the tailings would require the tailings dump to be classified as hazardous. “The test work we conducted was to im- prove recovery of ultra-fine material from

Wet High Intensity Magnetic Separators (WHIMS)

magnetises the yoke and f inal ly the matrix ring. The paramagnetic matrix material behaves like a magnet and at- tracts the fines. The ring is rinsed when it is out of the magnetic field and all the magnetic particles are carried into a magnetised launder within the rinse water. This technology also employs unparal leled high gradients to al low recovery of fine material down to 15 μm. WHIMS was special ly adapted by Multotec to accommodate the demands of the African environment. This has resulted in highly specialised magnetic separat ion equipment that comple- ments and enhances Multotec’s existing solutions offering. WHIMS is ideal for Ilmenite recovery and Silica sand cleaning and for the re- covery of fine, weakly magnetic minerals from slurries. www.multotec.com

26 ¦ MechChem Africa • March-April 2022