COVER STORY
Redefining gold processing economics
Across the global gold industry, processing plants are finely tuned circuits. Leaching circuits are designed to strike a careful balance between recovery efficiency, throughput, reagent consumption, capital intensity, and operational stability. Under these constraints, they perform remarkably well. Yet even in the most optimised operations, a reality remains: a measurable portion of gold exits the plant in as-arising tailings.
AZTEC Upflow Reactor Plant in Operation.
A cross the global gold industry, processing plants are finely tuned circuits. Leaching circuits are designed to strike a careful balance between recovery efficiency, throughput, reagent consumption, capital intensity, and operational stability. Under these constraints, they perform remarkably well. Yet even in the most optimised operations, a reality remains: a measurable portion of gold exits the plant in as-arising tailings. This is not a flaw in design or performance. It is the natural metallurgical limit of conventional leaching systems. What has traditionally been accepted as unavoidable loss is now being re-evaluated. The gold left in the tails represents a steady stream of unrealised value. Today, a new generation of intensified recovery technology is challenging long-held assumptions about what constitutes “final” recovery. The hidden gold stream Modern gold plants are engineered for efficiency. Tank volumes, agitation, cyanide dosage, carbon management and residence time are all optimised within economic and physical constraints. As a result, tailings typically retain residual gold values — not because the gold is unrecoverable, but because conventional systems have reached their practical threshold. For many operations, the cumulative value contained in as-arising tailings can equate to a meaningful percentage of annual production. Unlike historical tailings retreatment projects, this material is already within the active process stream. It requires no additional mining, no new crushing
circuits, and minimal incremental materials handling. The opportunity lies in completing the leaching and adsorption process, rather than restarting it. Completing the circuit AZTEC Mining, a technology-driven engineering company, has positioned itself at the forefront of this shift with its flagship technology: the AZTEC Upflow Reactor (AZ-UFR). Rather than replacing conventional leach circuits, the AZ-UFRs are installed downstream as a scavenging circuit. The AZ-UFR’s purpose is simple in concept but sophisticated in execution — to create an intensified reaction environment that extracts additional gold from slurry that would otherwise report to final tailings. Inside the reactor, slurry flows upward through a controlled reaction zone engineered to optimise solid–solution–carbon interaction. This intensified environment promotes additional gold dissolution beyond what is achievable in standard circuits. The result is incremental recovery without altering the upstream plant configuration. Because the AZ-UFR operates as a scavenging circuit, integration is typically straightforward. Existing plant performance is maintained while overall recovery improves — an attractive proposition for operating mines. Recovery without expanding the mine By recovering additional gold from material already being
8 MODERN MINING www.modernminingmagazine.co.za | March 2026
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