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MEI Online: Plant Operation News: Africa: July 26th 2005


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:: Aflease Uranium Plant to Utilise Pressure Leaching

Bateman has been contracted to carry out the metallurgical process design for the new uranium plant for Aflease Gold and Uranium Resources (previously Afrikander Lease Limited) to be located next to the company's existing Bonanza gold-mining operation in the Klerksdorp area of South Africa.

The basic costing and design for this project, which commenced in October 2004, has been completed. The plant will process ore mined from the Dominion and Rietkuil uranium deposits, which contain potentially in excess of 136 000 t uranium oxide and represent about 6 % of the world's uranium resource. The uranium oxide production rate will be 1800 t/yr giving an effective life of resource of 75 years.

The uranium plant will make use of pressure leaching in preference to atmospheric leaching for the enhanced overall uranium recovery. In addition to higher recoveries, pressure leaching reduces consumption of sulphuric acid due to the oxidation of pyrite in the ore, eliminates of the need for manganese dioxide as an oxidan, and reduces the leach residence time from 18 to two hours. The precipitation of excess iron in the leach autoclaves, is also reduced, thereby minimising the amount of iron build-up in solution.

The design criteria have been based on the original Afrikander Lease uranium plant, Rietkuil, which was one of the world's first oxygen pressure leach plants and was commissioned by Anglo American in 1982 but mothballed soon after commissioning. While Bateman has retained the basic design of the Rietkuil plant, improvements have been introduced into the mechanical design of the pressure-leach autoclaves. These improvements, gained from mechanical developments over the past 20 years, will enable the vessels to operate at higher temperatures than in the past. Improvements to the autoclave agitation, feed system and discharge system have also been incorporated.

After the pressure leach and subsequent counter-current-decantation and solvent-extraction stages, ammonium diuranate will be precipitated as yellow cake.




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