Technical Details
  • Alkaline/ammonia leach
  • Proprietary two stage leaching process
    • Ore specific cure/pre-treatment stage
    • Heap or tank leaching
  • Proprietary solvent extraction step to avoid ammonia carry-over into solvent
  • Uses conventional equipment
    • Electro-winning is identical to conventional acid circuits
    • Replacement acid leach in current operations
    • Minimal changes to plant
    • Higher organic transfer efficiencies requires smaller plant
  • Environmental benefits – ‘green’ process for a ‘green’ metal:
    • Reduced transport/shipping impact and costs
    • Minimal likelihood of AMD

AmmLeach® – Advantages I

Parameter Acid AmmLeach®
Mineralogy Oxides, carbonates, silicates, some sulphides Almost any – dependant upon curing stage
Curing Concentrated H 2 SO 4 Tailored to ore mineralogy
Selectivity Low- iron, manganese, calcium and silica are likely problems High- no iron, manganese, calcium or silica dissolution
Rate of extraction Limited by acid strength and diffusion Ammonia concentration in leach solution matched to leaching rate
Recovery 80% of leachable 70-80% in 130 days typical
Heap lifetime 55-480 days ~80-130 days typical
Sulphate precipitation Reduced permeability in heap, break down of clays and plant scaling due to precipitation of gypsum and jarosite Calcium and iron solubilities too low for precipitation, also low sulphate levels in leach solution

AmmLeach® – Advantages II

Parameter Acid AmmLeach®
Leachate consumption Depends upon carbonate content 3.7-27 kg/t reported Depends on concentration used, field trials show less than 1kg/t
Safety Concentrated acid required Gaseous ammonia main hazard, on – demand systems using hydrolysis of urea minimise transport risks
Precious metals Heap to be neutralised before cyanidation Neutralisation not required, potential for simultaneous recovery using thiosulphate or sequential leaching using cyanide
Mine closure Heap requires washing, neutralisation and long term monitoring to avoid AMD Heap can be washed and left, residual ammonia acts as fertiliser for vegetation regrowth, minimal likelihood of AMD.