Wayne Stange has 25 years of technical and management experience in the mining and minerals industry, as well as in other asset-intensive industries such as oil & gas and electrical utilities. Wayne has a deep understanding of comminution, flotation/recovery and has applied state-of-the-art simulation systems and modelling combined with data-based approaches to the design, operation, and optimization of integrated flowsheets. He has worked across a range of commodities—gold, platinum, base metals, copper, iron ore, mineral sands, and others—and has profound expertise in steady state and dynamic simulation for integrated metallurgical process and process-control design, operational de-bottlenecking, process control strategies, and plant operator and metallurgical staff training.
In Situ Leaching – Disruption or Distraction?
Currently metals extraction is accomplished via mining, minerals processing, metals extraction, tailings storage and waste disposal. Regardless of orebody value, at some stage, the mine or pit will reach a depth where the reward for mining wider and / or deeper is not justified by the anticipated returns. As a result of these issues, in-situ leaching (ISL) is being reinvented as a technology that could add value by extracting metals from ores more cheaply, with less environmental impact and using far less energy than conventional mining.
ISL has been employed selectively in the minerals industry for some time. For example, the production of potash and metals such as uranium, rely heavily on this approach. ISL only recovers the valuable product and negates the need for haulage, comminution and smelting of the ore body, thereby reducing the production of tailings. Without the need to dispose of waste rock and mineral tailings on the land surface, mine footprints can be dramatically reduced. A smaller workforce is required, and they will have less exposure to hazards of working underground or at opencast mines.
With all its benefits, why has in situ leaching not taken the world by storm? Several difficulties remain. Deep in situ (bio)mining will no doubt arouse similar concerns to those created by the hydraulic fracking of shale gas. Both processes involve pumping chemicals through the water table deep into the ground. Social acceptability remains to be developed. Also, applicable legislation does not exist in many jurisdictions. For hard rock copper and nickel sulphide ores and gold ores, the use of ISL remains in the experimental stage due to insufficient metal recoveries and long leaching times, making the method uneconomic. A step change is required. Will the game changer be in the form of better drilling, or increased blasting efficiencies, reduced acid concentration or a different acid, different management techniques, or a different leaching chemistry altogether?