A thickening technology is currently being designed by Outotec for First Quantum Minerals’ Kolwezi US$550 million-plus project in the Democratic Republic of Congo.
The thickeners, due for delivery and installation at Kolwezi in early 2009, include nine high-rate and high compression thickeners for the cobalt and copper tailings project.
“The delivery follows Outotec’s earlier successes in Africa with First Quantum Minerals in their Zambian operations at Kansanshi (similar supply scope) and with Frontier in the Democratic Republic of Congo, Guelb Moghrein in Mauritania and Bwana Mkubwa in Zambia”, says Outotec’s Australian Thickener Manager, Duncan Wyatt.
“The strength of our relationships in Africa is testimony to our thickening technology, ability to supply and support customers/projects in remote locations and the fact that Outotec’s global reach ensures even remote projects such as this are supported by local and highly experienced Outotec offices. The expertise and customer focus of our thickening team also played a vital role in this project.”
Outotec’s technology for the Kolwezi project includes a 42m pre-leach high-rate thickener with new generation vane feed well and a Directional Autodil feed dilution system. The new Directional Autodil system will be integrated with Outotec’s vane feed well system.
“The Directional Autodil system, has demonstrated advances in flocculant dispersion and effective feed dilution. The system has also undergone rigorous CFD testing by Australia’s CSIRO. The system will be applied in the Kolwezi project, which is expected to reach an annual production capacity of 5,000 tonnes of cobalt and 30,000 tonnes of copper for 50 years,” explains Richard Triglavcanin, Outotec’s Global Manager Thickening Technology.
“The technology is a significant advance because, other than some minor design changes, feed wells in high-rate thickeners have changed little in the past 15 years”.
“Modern high-rate thickeners generally incorporate some form of internal dilution into the feed well to dilute the feed and improve flocculation. The Directional Autodil advances this process by delivering dilution water into the feed well in a controlled manner based on feed density so that it complements the flow of the slurry feed.
“There is, therefore, a strong flow pattern within the top half of the feed well, ensuring optimised mixing of high density slurry feed and dilution water, together with flocculant.
“The shelf and vanes of this innovative design produce both upper and lower zones in the feed well. Vanes on the angle act as baffles to enhance mixing and dissipate the energy of the incoming flows. The bottom half of the feed well is less turbulent and ideal for aggregate growth prior to exiting the feed well,” says Triglavcanin.
The resource that underpins the long-life, low-cost Kolwezi project consists of stockpiled tailings from a mineral concentrator that processed high-grade ore from surrounding mines from the 1950s. Because of the poor recoveries obtained from conventional concentrating techniques, valuable amounts of copper and cobalt were discharged into two tailings dams that will be mined using high-pressure water guns, or monitors.