Reusable Heap Leach Pad

Reduce operating costs and environmental impact with a Resuable Heap Leach Pad

Reusable Heap Leach Pad
  • Description
  • Operation

A reusable, or on-off, leach pad is a relatively simple concept. Fresh ore is brought onto a dedicated prepared surface, stacked, and then leached. Once the leach process is completed, the spent ore is removed, making way for more fresh ore. As the spent material is reclaimed, typically with a bucket wheel excavator, the stacking system places fresh ore in the reclaimed area.

The stacking and reclaiming systems work together, with the stacker following the reclaimer as it moves around the pad. The concept is effective because the equipment can move without significant preparation work or support equipment.

Reusable Pad Benefits
The reusable pad has several advantages:

  • Grading and placement of a drain layer and impermeable liners are all costly. These can cost up to US $25 per square meter. If a pad is reused, those costs are limited to a comparatively small area. Limiting the size of the prepared area saves construction costs.

  • Solution control is less complex on a reusable pad since the pad has well-defined limits within which the solution can be placed. Since the pad is smaller, solution pumping distance and pump size are reduced, leading to the need for less piping. This results in both lower capital and operating costs. Since stacking is limited to a single rather than multiple lifts, power is not needed to pump solutions up tall steep grades, also leading to operational savings.

Applications

El Abra
Project
El Tesoro
Project
Radomiro Tomic
Project
Zaldivar
Project

At Mina Sur, as the stacker builds the lift it places material behind itself on the pad. The stacker never travels on the placed material, which limits compaction. This is an advantage as it enhances proper percolation of the leached solution and avoids the need to rip the pad surface. If the ore is compacted, the solution channels through the pad, leaving some areas where valuable metal isn’t recovered.

When retreat stacking is employed, there is little traffic on the pad. If there is traffic, it is usually limited to four-wheel quad runners and the personnel necessary to move and service the solution lines. In these instances, the ground bearing pressure is relatively low at about five psi (34 kPa).

Together, these combine to maximize the recovery of metal from the ore. Careful placement of the material, agglomeration to control fines and prevention of solution channeling are important factors in getting the best recovery from the ore.