Recovery of gold from gold ores has been driven by the available technology and its configuration in the process plant flow sheet.
Conventional practice in test work programs has the ore being ground fine (to 106 or 75 microns) to ensure liberation ahead of leaching or flotation. This paper identifies that, in many cases, gold and gold sulfide carriers will liberate and be recovered to a concentrate at much coarser sizes.
There is an exponential increase in energy consumption relative to particle size reduction. This impact becomes extreme when comparing crushing a product to 1 mm against grinding to 75 microns.
The resultant reduction in energy consumption when liberating and separating at 1 mm or coarser compared to grinding to 75 microns can be in the order of 15 kWh/t or 60 per cent of energy in the comminution circuit.
Recovery of free gold and gold sulfide carriers by preconcentration (using continuous gravity devices such as the InLine Pressure Jig), combined with flotation of the fine gold and gold carriers, can result in significant power savings.
There are multiple locations within the flow sheet that can be targeted using this process, including recovery in the cyclone underflow of existing plants, preconcentration ahead of the plant or complete greenfield, low-energy process plants designed from first principles based on data from a Gekko developed test work regime.
We will describe the process of defining mineralogy in the laboratory and the decision-making process through to actual applications in the field.
Several examples will be
provided, including a South African Witwatersrand gold ore, several Australian
gold ores and others, indicating the benefits of this process and where it has
been brought to commercial reality.
Gray, A H, Davies, M and Theletsane, G, 2014. Coarse
liberation and recovery of free gold and gold sulfide carriers for energy
reduction in process plants, in Proceedings 12th AusIMM Mill Operators'
Conference 2014 , pp 117–128 (The Australasian Institute of Mining and Metallurgy: Melbourne).