The ERA - Ranger Mine ore processing operation consists of a sulphuric
acid leach followed by counter current decantation and solvent extraction
circuits. The most expensive unit processing operation at Ranger is the
sulphuric acid leach. In 1992 and 1993 changes were made to the operation of the leach
circuit. These changes have reduced power and reagent consumption in
leach by 30 per cent and 20 per cent respectively with minimal effect on
extraction efficiency. The first change was to operate the leach circuits at higher pHs than
previously attempted. In addition a cap was placed on the amount of acid
added to the leach circuit. Secondly, an on-line pH measurement system
was installed and has reduced the variation with time of the leach circuit
pHs. Finally, the number of leach vessels used was reduced from ten to
seven. This action was undertaken after an examination of the uranium
profile and the residence time in the leach circuit from previous years. This paper examines the above changes and assesses their effectiveness
on plant performance and costs.