When one of the world’s largest copper and cobalt producers wanted to double its production rates, it chose FLSmidth to provide a thickener solution that included six of its proven high density thickeners. The order was placed in 2020, and delivery has been completed.

The mine, located in the Democratic Republic of Congo (DRC), already had FLSmidth thickeners on site, and was satisfied with their performance. According to FLSmidth general manager projects and account sales Howard Areington, the company’s proposal for the mine’s expanded requirements was based on testwork to confirm the characteristics of the material that would be treated.

“The tests confirmed that we could use a similar design to what we had installed on the mine some years previously,” he says. “This solution included six counter current decantation (CCD) thickeners and one pre-leach thickener, each measuring 31 metres in diameter.”

These units deliver high solids underflow to optimise the recovery of dissolved metals. In addition to the steeper floor slope, these FLSmidth thickeners were designed with a high torque ring gear drive design, with high tolerances that make for minimal maintenance over long periods of time.

“Our high density thickener design ensures consistently high underflow densities which allows the operator to sustain high production rates and better recoveries,” he says.

These CCD thickeners are manufactured from LDX2101 duplex stainless steel. This provides mechanical benefits without compromising chemical resistance, allowing the mass of each unit to be reduced. The pre-leach thickener, which was not exposed to corrosive conditions, is constructed from carbon steel.

“We also designed and supplied five impurities removal thickeners, which are high rate thickeners, also in LDX2101 stainless steel,” he says. “The sizes of these units ranged from 20 to 30 metre in diameter.”

Fabrication of the equipment was done in South Africa, while accommodating the demands of the Covid-19 lockdown, which required careful planning and flexibility. With components and platework delivered to site, the welding and construction was conducted by the mine with installation assistance from FLSmidth and its agent in the region.