The Three Core Processes of Heap Leaching Gold Extraction

Heap leaching is widely recognised as one of the most economical methods for extracting gold from low-grade ore due to its significant advantages of low investment and minimal costs.

This process involves constructing piles from crushed ore, employing a spray system to ensure uniform penetration of the leaching solvent. Following chemical reaction with the gold, the gold-bearing solution is collected from the base of the heap, ultimately achieving gold recovery. The efficacy of a heap leaching system hinges on the precise design and control of three critical stages: heap construction, solution distribution, and solution recovery.

I. Scientific Heap Construction: The Foundation of Stability and Efficiency

Heap construction constitutes the initial stage of heap leaching, directly impacting subsequent leaching efficiency and operational safety. This process necessitates comprehensive consideration of site selection, heap stability, material particle size, and construction equipment. For large-scale permanent heap leaching sites, layered construction is commonly employed. This involves continuous layering without removing preceding strata until the operational lifespan concludes.

Regarding equipment selection, alongside flexible truck-based transfer systems, mobile belt conveyor systems are gaining prominence due to their high efficiency and uniform material distribution. This represents the developmental trajectory for achieving large-scale, high-efficiency heap construction. 

II. Precise Solution Distribution: The Key to Leaching Reaction

The liquid distribution system's function is to uniformly and stably disperse solutions containing leaching agents such as cyanide across the ore heap surface. Current mainstream distribution methods include spraying, dripping, and atomisation. Among these, rotating oscillating spray nozzles are most widely used, offering advantages of even coverage and reduced clogging. However, they present issues such as droplet impact on the heap surface and solution evaporation losses due to wind effects.

In contrast, drip systems effectively enhance heap permeability with minimal solution evaporation, though they demand higher water quality and anti-clogging standards. Atomised distribution increases dissolved oxygen levels, facilitating certain oxidation reactions. The future of distribution technology lies in developing novel methods and achieving automated, precision control systems.

III. Seepage Prevention and Collection: Safeguarding Security and Recovery

The solution collection and seepage prevention liner system constitutes the lifeline and environmental core of heap leach pads. This system primarily comprises a seepage barrier layer, a valuable liquid collection layer, and a leak detection layer.

Seepage Prevention Liner: Typically composed of multiple layers of geosynthetic materials, its fundamental purpose is to absolutely prevent the leakage of highly toxic cyanide-containing valuable liquids, thereby protecting groundwater resources.

Precious Liquid Collection: Above the liner, a permeable layer of graded gravel and a collection pipe network are installed. Precious liquids within the heap flow gravitationally along the liner gradient (typically ≥0.5%) towards collection channels and pipes, ultimately draining into precious liquid storage ponds. Scientific design effectively prevents liquid stagnation or channel erosion, ensuring heap stability.

As mineral resources become increasingly ‘poor, fine-grained, and complex,’ heap leaching will assume greater significance. Future advancements in efficient heap construction equipment, optimised liquid distribution control, and enhanced impermeability and leak detection technologies will ensure heap leaching continues to drive the efficient development of low-grade gold resources. This approach guarantees safety and environmental protection while achieving a dual win for economic and ecological benefits.