Commercial application of membranes at Kayelakera and Langer Heinrich

Both the Kayelekera and Langer Heinrich uranium mines (both mines developed and operated by Paladin Energy Limited) incorporated innovative process technology in their original design. Kayelekera incorporated continuous RIP extraction and Langer Heinrich incorporated alkali leach and RIX. These two mines were the only new mines to be successfully developed by a non-state operator in the last uranium price boom (post 2000 and pre Fukashima). Both operations incorporated some sub-optimal design issues that increased operating cost and reduced operability. One of the assigned rolls of the Paladin Technical and Project Development team was to develop cost effective resolutions for such issues. At the Kayelekera Uranium Mine (Malawi), acid demand for uranium leach and resin elution was throughput limiting, so a strategy to improve this situation was sought. The solution selected was to introduce a nano filtration circuit into the concentrated eluate processing section. Through nano filtration, a significant portion of the acid used for resin elution was able to be recycled back to the process without material accompanying recycle of uranium. The Langer Heinrich Uranium Mine (Namibia) utilises RIX for uranium extraction and impurity rejection. Resin ageing in the presence of alkali process liquors was a material issue, leading to the gradual decline of resin adsorption capacity and effective loaded resin uranium tenors. This necessitated a gradually increasing resin advancement (and elution) rate. Loaded resin in this process is eluted with 1M sodium bicarbonate, which ultimately leads to a gradual increase in sodium carbonate concentration in process liquors, to the point that sodium carbonate becomes a circuit poison. Nano filtration was again able to be used to recycle a significant portion of the elution sodium bicarbonate back to barren eluate make-up without material accompanying uranium. In both the above cases, process operating costs were reduced materially, especially so in the case of the Langer Heinrich mine, where total process operating costs were reduced by over 50% (cost per pound U₃O₈ basis). (author)