Gekko has announced the purchase of an InLine Leach Reactor (ILR) for the Bulyanhulu gold mine, in the north-western region of Tanzania within the Kahama district, an operation under the ownership and management of Barrick Gold.
The introduction of the ILR to this location is a significant development, building upon the success of its implementation at various other mines operated by Barrick, including Hemlo, Kibali and Loulo-Gounkoto, Gekko says.
The ILR’s innovative design and efficient mineral leaching chemistry is providing high gold recoveries and production improvements to many operations worldwide, Gekko says. ILR orders have continued to respond positively to strong gold prices, with interest from a range of milling operations across the globe including North America, South America and Africa.
The ILR can be retrofitted into any gold grinding circuit, with the unit receiving gravity concentrates or flotation concentrates into a fully enclosed rolling drum. Inside the drum, the ore concentrates are mixed typically with a 1-2% sodium cyanide solution and an oxidant, known as intensive leaching. Specialised baffles inside the drum keep the solids in constant contact with the chemical solution providing a high shear environment. The correct combination of chemicals and concentrate, plus the rolling action of the drum, creates a highly efficient leaching reaction, Gekk0 says. This drives faster kinetics primarily through mixing and attrition which is critical to remove the oxidation layer away from the surface of the gold particles and allow enriched solution containing the required reagents to access fresh. Leach rate can be directly correlated to the attrition energy absorbed, according to Gekko.
Lifters inside the ILR drum mechanically agitate the slurry, forming an oxidant-rich zone with high solids-liquids mixing for leaching. Gekko says it has conducted multiple comparisons on the scale-up between bottle rolls and site data, consistently demonstrating that the ILR has performed equal to, or in some cases better, than laboratory bottle rolls.
The Batch and the Continuous ILRs work to chemically leach metal from ore concentrates using the same leaching principle. The ILR’s horizontal “rolling bottle” design keeps the concentrates in suspension and continuously mixes to accelerate the chemical reaction within the solution. The rolling bottle provides a pure mixing zone, preventing the risk of the solution short circuiting, the company explains.
When leaching in the batch units is complete, the pregnant ‘metal-rich’ solution is clarified and transferred to an electrowinning circuit. With the continuous units, there is an additional process route. The options include the pregnant solution reporting to carbon columns, resin columns, Merril Crowe circuits and in some cases direct electrowinning can still be applied. The barren residual solution can report back to the circuit, detoxification process, recycled or in some cases a combination is applied.