Bateman embarks on engineering, procurement on the worlds first alkaline heap-leach uranium mine
By: Jonathan Faurie 2nd July 2010
South African engineering company Bateman Engineering has embarked on engineering and procurement for the Maxi phase of the greenfield Trekkopje uranium project in the heart of Namibias Namib desert.
French nuclear giant Areva, through its subsidiaries, Areva Resources Namibia and Areva Processing Namibia, is developing the worlds first uranium mine to make use of an alkaline heap-leach process.
Owing to the unique nature of this alkaline leach application, Areva is developing the Trekkopje project in three distinct phases the Mini, Midi and Maxi projects covering the technology demonstrator and the industrial and full-scale process development stages.
The Midi project, for which Bateman was the engineering, procurement and construction management contractor, is currently being handed over to Areva.
Batemans scope of work for the Maxi project comprises the engineering and procurement related to the conveying of primary in-pit crushed run-of-mine ore, the comminution circuit, agglomeration, heap irrigation, reclaiming, interface management and site infrastructure.
The Maxi project is currently on schedule for first ore stacking in the first quarter of 2012, with engineering 40% complete and procurement 50% complete.
The Trekkopje deposit is a large, shallow and low-grade uranium resource. The life-of-mine is estimated at between 12 years and 14 years, mining at a rate of 36,4-million tons a year, or an average of 100 000 t/d. The expected production of U3O8 is 3 200 t/y, with the equivalent UO4, or yellowcake, tonnage slightly higher.
An integrated procurement strategy has been employed, using combined Areva and Bateman vendor databases. Before beginning procurement, an intensive value-engineering exercise ensured that the plant design was optimal in respect of capital expenditure, operational expenditure and functionality. This focused on reducing the installed redundancy and tight equipment specifications for maximum equipment availability and plant use.
While the procurement strategy was developed to ensure that all procurement was done from the best available global vendors and contractors, the strategy also aimed to increase the social footprint of Areva in Namibia by using Namibian contractors where possible.
Bateman and Areva are committed to best practice internal safety standards and this has been emphasised by incentivising a strong safety culture for all contractors involved on the project.
The Trekkopje Maxi project will be an openpit mining operation, followed by crushing, screening, agglomeration and a carbonate/ bicarbonate heap-leach process, which is, in turn, followed by ion-exchange UO4 recovery. The majority of the spent ore is planned to be stacked into the mined areas of the pit, with associated ongoing rehabilitation.
The heap-leach pad will comprise 30 cells in total, of which about 22 will be active at any given time, while the remainder will be in various stages of construction stacking, demolition reclaiming, or maintenance in line with the on-off heap-leach-pad method.
Prior to leaching, as much chloride material as possible will be removed from the four most recently stacked cells in a two-stage washing process, with the water being recovered for reuse in the washing process.
During the basic heap-leach process, uranium in the ore is dissolved by a solution of sodium carbonate and sodium bicarbonate reagents. The pregnant liquor solution is pumped from the pond to the back-end plant where uranium is recovered through various ion exchange, elution and precipitation processes, and the final product produced is yellowcake.
Once the leach cycles are completed, the ore is removed from the pad through a reclaimer system and disposed through a spent-ore facility. Edited by: Martin Zhuwakinyu
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