A reusable, or on-off, leach pad is a relatively simple concept. Fresh ore is brought onto a dedicated prepared surface, stacked, and 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.
The reusable pad has several advantages. Grading and placement of a drain layer and impermeable liners are all costly, up to US$25 per square meter. If a pad is reused, those costs are limited to a comparatively small area. So 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, and less piping is required. 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.
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