Following installation of new Multottec HX3
and HX5 spirals similar to that shown here,
Northam’s plant yield increased from 21%
to almost 30%.
New Spirals Boost Recovery at Northam Chrome
The decision to replace the existing spirals was taken by the chrome producer following extensive testwork performed by both Northam and Multotec. Results from the testwork, said Multotec, indicated that its spirals outperformed the competitor units installed in the plant. Testwork was later revalidated at Multotec’s in-house technology division in Spartan, Gauteng, South Africa, according to the company.
Based on the outcome of these trials, Northam Chrome Producers decided to replace the existing spirals— which had reached their end of life—with Multotec spiral technology. “Tests showed that by using the Multotec spirals, the plant would be able to increase recoveries by an additional yield of 6%,” said Multotec’s Graeme Smith, who noted that his company removed 172 spiral assemblies from the existing recovery plant and replaced them with 72 Multotec spiral assemblies. These comprised Multotec HX5 and Multotec HX3 spirals with feed tonnage capacities ranging from 4–9 metric tons per hour (mt/h) per start.
Smith said one of the biggest challenges of the two-month project was retrofitting the new spirals into the existing structure. This required extensive work by Multotec’s in-house drawing office, which undertook all the drawings and confirmed the new layout of the plant, while also presenting the modifications needed to the structure to accommodate the new installation.
The project was overseen by Smith and field service technician, Raymond Masinga. “The commissioning of the plant was an easy exercise. It started up the same day and immediately started outperforming the earlier test results,” Smith said. He reported that the entire plant’s yield is now closer to 30%, compared to the average of 21% in 2014. Multotec engineers determined that the cost of the spiral assembly is about 0.004c/feed ton, with Northam Chrome Producers expected to see a return on its investment within a four-year period.