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Company Announcement: FLSmidth's Counter Current Decantation Circuit at Husab will be the Biggest in Africa

19th June 2013

By: Creamer Media Reporter

  

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FLSmidth  (0.05 MB)

Swakop Uranium’s new counter current decantation (CCD) circuit, designed and supplied by FLSmidth for the mining company’s new Husab Project, will be the biggest of its kind installed on the African continent to date. Located near Swakopmund on the west coast of Namibia, the Husab Project is the largest in-situ and highest grade, granite-hosted uranium deposit in Namibia, and currently the third-largest uranium-only deposit in the world. Swakop Uranium is jointly owned by Taurus Minerals Limited of Hong Kong (90%) and the Namibian state-owned mining company, Epangelo (10%).

CCD thickener circuits are used to recover soluble metal as pregnant liquor solution from ore leach residue. The basis of CCD operation is to concentrate suspended solids, thereby minimising liquor content in underflow slurry that flows in one direction. The underflow slurry liquor is then diluted with wash liquor that flows in the opposite direction, while the suspended 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 scope of the FLSmidth order for the Husab circuit comprises seven 40 metre diameter thickeners, of which one is a high density pre-leach feed thickener and the other six are high rate CCD thickeners. FLSmidth is also supplying one 25 metre diameter ADU (ammonium diuranate) high rate thickener for installation further down the process.

“Based on our extensive experience in CCD circuits and on test work we’ve conducted on the leach feed, we were able to propose smaller diameter thickeners than the 50 metre diameter units originally specified by the client,” Mark Sheward, FLSmidth minerals business development manager, says. “We were so confident that 40 metre diameter units would work better that we’ve offered the client a process guarantee in this regard.

“Our latest test work campaign showed that by using 40 metre diameter high density thickeners with our proprietary P-Duc™ Feed Dilution System, both pre- and post-leach slurries settled extremely quickly and reached the desired underflows in a very short period of time. Effectively, this means that we can achieve higher rise rates — which are the effect of reducing thickener diameter — while still achieving the required underflow residence times.

“There are several benefits arising from this option, including a reduced overall capital cost of the thickeners and reduced site erection time which is associated with cost savings and may also assist in achieving an earlier plant commissioning date. In addition, the raw material costs associated with 40 metre diameter thickeners, compared to 50 metre diameter units, are significantly less, considering that the material of construction chosen for this installation is imported LDX2404 duplex stainless steel capable of handling the acid leach. The civils will also be completed faster with 40 metre diameter thickeners. The overall plant will be smaller, resulting in savings on piping, walkways, pipe rack and services. 

“Ultimately we’re looking at saving up to a third of the costs calculated for the original thickeners specified and probably the same amount on the civils and installation costs.” FLSmidth’s P-Duc Feed Dilution System is the next generation of forced dilution technology and has been designed to offer all the advantages inherent in the company’s original E-Duc feed dilution system, as well as the ability to optimise the feed dilution over a wide range of feed stream densities. This new generation of FLSmidth feed dilution technologies can now cope with a wide range of feed densities and flow rates, while still delivering optimum density in the feedwell.

The company’s e-volute feedwell system arrangement will also be utilised on the Husab Project, offering a number of advantages, such as minimising floc shear and achieving an even spread of material throughout the surface area. “We’ve delivered a number of smaller reference CCD circuit installations in the Southern African market in the past five years, both in uranium and in copper processing plants,” Sheward says. “This high order rate can be attributed to the quality of our process support pre- and post-award, timeous delivery of the equipment and the quality and unique technological advantages possible with this equipment.”

FLSmidth, a leading single-source supplier of complete plants, equipment and services to the global minerals and cement industries, will deliver units to the Husab Project between April and August 2014 and will provide technical and commissioning assistance. Operational and strategic spares are included in the contract. For the manufacture of this order, FLSmidth is following its standard global sourcing strategy. Detail design and engineering was conducted at the Group’s Minerals Technology Centre in Utah, USA and the tanks will be manufactured in sections in South Africa, with proprietary thickener drives being supplied from FLSmidth in Germany.

Edited by Creamer Media Reporter

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