First Operational Leachox™ System
The Leachox™ Refractory Gold Process – The Testing, Design, Installation and Commissioning of a large Scale Plant at the VASGOLD Gold Mine, Kazakhstan. Presented at the MEI Precious Metals ‘10 Conference, Falmouth, Cornwall, UK, June 2010.
Agnes Gold Mine
The first Leachox process plant was supplied under a contract licence arrangement to the Agnes mine in South Africa owned by African Pioneer Mining. The Agnes mine had previously been unsuccessful in using a bio-heap process to treat the refractory gold ore. Reasons for the low recoveries obtained from the bioprocess were given as poor adhesion of the concentrate to the substrate in the coating system, the concentrate having high levels of carbonate and problems related to the permeability of the heap due to the sub-tropical nature of the site i.e. heavy summer rain storms washing concentrate off the substrate and channels forming in the heap. The mine was put on care and maintenance. Leachox was brought in to treat the high grade tailings resulting from the heap for approximately a one year period. The tailings generally ranged in grade from around 20g/t to 25g/t Au but often material over 35g/t Au was treated. Leachox achieved recoveries higher than 85% on this material with cyanide, oxygen and lime consumptions of around 4 kg/t, 10 kg/t and 10 kg/t respectively. Direct cyanide leach on the tailings (i.e. without Leachox) only gave recoveries in the range 15 – 20%.
Transvaal Gold Mining Estates
Simmer & Jack have leased a hybrid Leachox system for their TGME operation near Pilgrim’s Rest in South Africa. The Leachox plant, which is run by MMS on contract, treats approximately 30% of the refractory ore entering the plant depending on the nature of the ore being mined. The leased equipment includes an Imhoflot G-Cell circuit for the removal of preg robbing carbonates, a G-Cell circuit for the recovery of sulphides and a hybrid Leachox Aachen Reactor circuit in combination with a Deswik stirred ultra-fine grinding mill. Even with only partial treatment with Leachox recoveries have improved by over 50% of those previously obtained.