Heap leaching is a low-cost hydrometallurgical method for recovering gold, silver, copper, and uranium from ore. Crushed ore is stacked on an impermeable liner and irrigated with a chemical solution (typically dilute sodium cyanide for precious metals) that percolates through the pile, dissolves the target metal, and is collected at the base for downstream recovery in an ADR or Merrill-Crowe plant.
How It Works
The process has five steps: (1) crush ore to a target size (typically 1/2 to 1 inch for gold), (2) agglomerate with cement or lime to bind fines and stabilize permeability, (3) stack the agglomerated ore in lifts on an impermeable HDPE-lined pad, (4) irrigate with dilute cyanide solution via drip emitters or sprinklers, and (5) collect the pregnant leach solution (PLS) in a lined pond for recovery in an ADR or Merrill-Crowe plant.
When to Use It
Heap leaching is the economical choice for large-tonnage, lower-grade gold and silver deposits where milling would not return capital. It also works for copper oxides and some uranium ores. Recovery typically ranges from 60% to 85% depending on ore character — lower than milling, but at a fraction of the capital and operating cost.
Key Design Parameters
Crush size (driven by column-leach kinetics), heap height (typically 6 to 60 m in lifts), irrigation rate (typically 8–15 L/h/m²), cyanide concentration (typically 200–500 ppm NaCN), and total leach cycle time (60–365+ days). All of these are project-specific and determined by laboratory column leach testing.
The KCA Heritage
KCA engineered our first heap leach at Manhattan, Nevada in 1972 — only the third heap leach in the world. We have since delivered over 500 heap-leach engineering projects across six continents. See our heap leach plant design reference for full technical scope.
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