The processing phase of the operation starts at the ROM pad and is completed at the Port of Townsville where the copper bundles are cleared for overseas shipping. 

Ore is fed by a front-end loader into a 500 tph 2-stage crushing and screening plant consisting of a jaw crusher and a cone crusher in closed circuit with a vibrating screen.  The final product size is 80% passing 19mm.

The crushed material is then passed through an “agglomerator” where sulphuric acid (“H2SO4”) and water is added. This starts the leaching process and causes the finer particles to adhere to the coarser ones, which is essential for the creation of permeable heaps.  The ore is then discharged from the agglomerator onto an overland conveyor which transports the ore to the heap stacking system.  The stackers build heaps about 80m wide x 350m long x 6-8m high each containing about 250,000t ore.

Once the heaps are built they are then irrigated with dilute sulphuric acid at a rate of 8-12 litres per hour per square metre of surface area. The solution passes through the heaps dissolving copper in the form of copper sulphate (“CuSO4”).  The copper laden primary leach solution (“PLS”) contains 4-5 grams per litre (“g/l”) Cu and is collected and flows to collection ponds via drains.

The PLS solution is then pumped to the solvent extraction process (“SX”) where the solution grade is increased to about 50 g/l Cu using a highly copper selective organic reagent.   The PLS and organic are vigorously mixed transferring the copper to the organic phase. This is called the “extraction” phase.

The depleted solution (“raffinate”) at 0.5-1 g/l Cu returns to the heaps to “reload”.  The loaded organic is then vigorously mixed with a highly acidic solution returning from the electrowinning (“EW”) tank house.  This agitation tranfers the copper again and creates a strong electrolyte solution (50 g/l Cu) to be pumped to the electrowinning phase of the process.  This is called the “stripping” phase.  The stripped organic returns to the extraction phase to “reload” and the resulting strong electrolyte solution is filtered and pumped to the electrowinning tank house.

The tank house contains 76 cells each containing 34 lead alloy anodes and 33 stainless steel cathodes.  A high amperage (22,000 amps) low voltage (1.5-2 v/cell) current is passed through the cells and causes pure copper to be plated onto the cathodes and oxygen to be liberated at the anodes.  The partially depleted weak electrolyte (35-40 g/l Cu) returns to the strip phase to “reload”.

Each copper plated cathode is stripped every 7 days with the resulting pair of cathode sheets each weighing around 50 kg.  These pure London Metals Exchange (LME) Grade A (99.999% Cu) cathodes are bundled in 3 tonne lots and transported to the Port of Townsville for sale to Glencore International, which has an offtake agreement with LAO for cathode production and export overseas.