Heap and In Situ Leaching

Leader: Dr Stephen Neethling

It involves a fluid known as a leachate flowing through heaps of crushed ore. The leachate and leaching conditions are chosen so that the valuable minerals will dissolve into the fluid, while the other minerals are left behind in the heap. Further processes are then used to extract the dissolved minerals from the solution. Rio Tinto is considering the use of heap leaching in several copper deposits under study, including La Granja in Peru.

The Centre’s leaching project, led by Steven Neethling, is looking at how to improve leach performance by refining 

liquid flow distribution. The first part of the research is using modelling techniques to predict how fluid will flow through ore heaps, and how to improve the design of leaching operations to get maximum extraction. The team is achieving this by producing realistic small scale heap structures for simulating flow.

“The leaching work is progressing very well,” said Jan Cilliers, “and I believe we are also looking at a timescale of five years to delivery.”

This work has the potential to develop methods for “in situ leaching” – leaching that takes place underground where mineralisation occurs. As the ore does not have to be brought to the surface, it can create significant savings in energy. With this approach the rock would have to be fractured first underground, which means this project connects to the Centre’s fracturing project.



Above: A simulation of multiphase flow through an idealised 2D channel network. The system is 10cm by 10cm.

Together, these processes would be important components of improving block cave operations. Block caving is an underground mining method that is of increasing focus for the industry. The process exploits rock’s natural fractures so that it breaks under gravity rather than by using explosives. It potentially makes mining cheaper and safer, and causes less disturbance at the surface. This means that resources could be developed that might not be exploitable by other means.