Acid consumption and the associated costs are a significant component of the operating costs at Kayelekera, accounting for ~14% of the C1 costs. Reducing acid consumption or improving acid recovery within the process, either via the installed nano-filtration plant or through improved recirculation, could have a significant impact on plant operating costs.
Not only is acid an expensive reagent, but the process itself is acid limited as the onsite acid plant has a maximum capacity of only ~235 tonnes per day sulphuric acid. By reducing acid consumption or recovering more acid, there is an option to maximise plant throughput and production, thereby consuming the additional acid or maintaining the same throughput but reducing the production of fresh acid and therefore related costs.
The acid recovery work has focused on improvements that can be made to the already installed nano-filtration circuit (recovers acid from the resin elution circuit) and improved recycling of acid within the leach circuit. Further work is also been done on investigating the benefits that ore sorting could have in terms of rejecting the high acid consuming barren minerals from the feed material.