MechChem Africa April 2020

An innovative hydrocyclone solution from Multotec is allowing a large Zambian copper mine to develop a safe and cost-effective tailings storage facility. Custom cyclone solution solves Zambian TSF challenge

T hetailingsstoragefacility(TSF)faced a number of challenges according to Frikkie Enslin, senior applications engineer, who is responsible for cyclones at Multotec, including its extensive planned capacity and the area’s flat topogra - phy. The mine’s process plant pumps some 10 000 m 3 per hour of tailings to the TSF, requiring its final circumference to reach about 19 km. “The flat area around the mine meant there was no suitable topography to provide a natural dam,” Enslin says. “It was therefore vital to create strongwalls to retain the slurry fromthe plant, so that the integrity of theTSF could be assured.” Simple gravity separation and sun-drying hadprovedunable to creatematerial thatwas firm enough to constitute walls. In the early days of the plant’s operation, it was shown that material being deposited by means of plain spigoting could still not be walked on after amonthof drying in the sun. By contrast, Multotec’s 250 mm GV hydrocyclones were able to deliver an underflow discharge that could be walked on in just two days. After a week,thematerialcouldwithstandtheweight of an excavator. The sheer volume of slurry being pumped into the TSF, however, created its own chal- lenge. The hydrocyclones had initially been mounted on metal cradles, which were in- undated within a couple of hours. Extracting the cyclone and cradle from the mud for the

next placement was difficult and very time consuming. “The client needed a solution that would keep the cyclone above the slurry level for longer, andwould be easier tomove,” he says. “To do this, we designed a cyclone cradle that could be attached to a long wooden pole, giv- ing greater height, allowing the customer to leave the cyclones in the same position for a much longer time.” With Multotec’s experience and facili - ties for custom design and manufacture, the hydrocyclones were then modified to be lighter. This made them easier to handle and manoeuvre. “Constructed with a lighter metal, these tailormade units are industry leaders as they are lightweight and are rubber-lined to en- sure long wear life,” he says. “We also made some innovative improvements to the vortex finders and the cone sections, which are now metal spun.” Other changes were made to speed up the changing of a spigot, and the moving of the hydrocyclones fromone point on the TSF wall to the next. The design now includes a threaded spigot coupling and quick-release connections on the cyclone. The solution has been so successful to date that over 250ofMultotec’smodifiedGV hydrocyclones have already been installed. “Just as we collaborated closely with the customer in developing this solution, so we continue our partnership in monitoring the

Frikkie Enslin, senior applications engineer, Multotec.

Multotec’s 250 mm GV hydrocyclones deliver an underflow discharge that could be walked on in just two days.

The cyclone cradle was attached to a long wooden pole giving greater height and allowing for it to be left in the same position for longer. performance of our hydrocyclones as the project goes on,” Enslin says. “An expert ap - plication engineer from our Johannesburg head office visits the site regularly, while our Zambia office in Chingola offers solid techni - cal and field service support.” q

The Multotec GV cyclones are designed specifically for tailings dam applications.

22 ¦ MechChem Africa • April 2020