The Counter Current Decantation (CCD) thickener circuit at Swakop Uranium’s Husab project demonstrates the potential of an FLSmidth package solution. Designed and supplied by FLSmidth, this CCD circuit has the largest diameter thickeners of its kind to be installed on the African continent in this type of application.
Located near Swakopmund on the west coast of Namibia, Husab will reportedly be the largest open-pit uranium mine in the world and will mine 150 Mt of rock and produce over 15 million pounds of uranium oxide annually.
FLSmidth 40 m diameter CCD thickeners installed for Swakop Uranium.
The shareholders of Swakop Uranium are the Republic of Namibia, through state-owned mining company Epangelo, and the People’s Republic of China, through state-owned CGNPC.
The scope of the FLSmidth order for the Husab CCD circuit comprises eight 40 m diameter thickeners, one of which is a high density pre-leach feed thickener and the other seven are high rate CCD thickeners. FLSmidth is also supplying a 25 m diameter ADU (ammonium diuranate) high rate thickener for installation further down the process. In addition to this, 38 Krebs® centrifugal pumps will also be installed in all slurry pumping applications on the project.
Significantly, such is FLSmidth’s confidence in the CCD thickener solution provided that the company has offered the customer a process guarantee in this regard.
Describing a CCD thickener circuit, Terence Osborn, Sales & Market Manager, Base and Precious Metal for sub-Saharan Africa at FLSmidth, says the technology is used to recover soluble metal as pregnant liquor solution from ore leach residue.
The basis of CCD operation is to concentrate the leached solids, thereby minimising liquor content in the underflow slurry that flows in one direction. The underflow slurry is then diluted with wash liquor that flows in the opposite direction, while the leached solids are concentrated repeatedly. The amount of liquor in the thickener underflow contributes to determining the number of CCD stages required to recover the desired amount of soluble metal.
The nature of the process means that pumps are integral to the CCD circuit as these transfer the solution and the slurry from one stage to the next. Slurry being transferred has a very high density which maximises the wash efficiency, making this type of application specifically suited to Krebs® pumping technology.
“The Krebs® pumps are well matched from a process performance perspective and the ideal pump for the transfer of material between the stages within the CCD circuit. Centrifugal pumps are capable of achieving the high flow rates required in this application and the Krebs® pump has the added benefit of its patented wear ring design which minimises wear enhancing pump performance and life,” Osborn says.
The tailings pumps, also supplied by FLSmidth, have been installed in series. These Krebs® slurryMAX™ pumps will facilitate the transfer of material over the extended distance from the process plant to the tailings storage facility.