Evaluación del método de Injection Leaching en la relixiviación de PADs para optimizar la recuperación

Resumen

Peruvian mining, crucial to the national economy, faces the challenge of optimizing gold recovery from depleted leach pads (DLPs), such as those at the Shahuindo mine in Cajamarca. This study evaluated the injection leaching method as an innovative solution to reactivate these residual resources. The research, conducted in two phases, began with a geophysical electrical resistivity tomography diagnosis that identified unleashed areas in Pad 1A, followed by the design of 31 injection wells and metallurgical tests that established 350 ppm of cyanide as the optimal concentration. Phase II (2023) covered the operational implementation of the process, with cell assembly, filter cleaning and controlled well rinsing. During the pilot phase (Dec. 2021-June 2022), 2,110 ounces of gold were recovered, bringing the overall recovery from the pad from 77.3% to 79.2%. In the operational phase (Dec. 2022-Mar. 2023), an additional 1,317 ounces were obtained. Comparison with conventional methods demonstrated the superiority of Injection Leaching, achieving higher recovery with 15 times less cyanide consumption (350 ppm vs. >2,300 ppm). In addition, the re-leaching operation in 2023 generated a return of more than USD 2.4 million, albeit with lower metallurgical efficiency. The injection leaching method is a viable, sustainable, and profitable technology that maximizes the extraction of residual gold through controlled, three-dimensional injection, positioning itself as the optimal alternative for exploiting value in historic stockpiles. Keywords-- Injection leaching, re-leaching, PADs, recovery, gold, optimization.