The following is an excerpt from The Miner, a quarterly magazine highlighting the work happening at the company’s North America mining operations and processing facilities. Read the full story in the latest edition.
If you’ve ever spent any time inside a greenhouse on a sunny day, you probably have some idea of how a sealed thermal barrier affects what’s under it. Things get a lot warmer. That’s the principle behind leach pad blanketing – or “covers” – as it often is referenced in discussions about Leach to the Last Drop.
In theory, every degree of temperature increase proportionally boosts copper recovery, and there’s enough data-driven confidence in testing that on a large scale at active operations. The thermal covering method was selected from a backlog of ideas not fully explored and now is in play across the organization as a critical component of the Leach to the Last Drop project, the objective of which is to get more copper out of stockpiles than was thought recoverable in years past.
Leaching teams across the company continue to refine this technique, intended to help accelerate copper recovery from newly placed ore, and squeeze more copper out of older ore piles.
“Based on theoretical analysis, it was assumed that heat would drive increased recovery from leach pads by helping the leaching solution dissolve the copper faster, said Todd Morman, Innovation Engineer II-Safford. “With that information coming out of the lab, there was a decision to start covering stockpiles, so it’s been a big initiative.”
Since November 2021, nine operations – Bagdad, Chino, Miami, Morenci, Safford, Sierrita, Tyrone, Cerro Verde and El Abra – have been covering sections of their active leach areas with clear plastic sheeting, which helps keep solar and chemically generated heat contained within the pad underneath.
High recover at low cost
“This has been a giant experiment,” said Cory Stevens, President, Freeport-McMoRan Mining Services. “We’ve gone across all the sites and put down about 30 million square feet - over 1 square mile in total area. That represents about 20 percent of our total leach area, which could deliver us 5 to 10 percent more recovery at low cost and low carbon output.”
Read the full story about the use of covers to generate heat for the Leach to the Last Drop initiative and other features in the current edition of The Miner.