Agglomeration is the process of binding fine ore particles together into larger, more stable agglomerates before stacking on a heap leach pad. The binder (typically cement, lime, or both) glues fines to coarser particles, improving heap permeability and preventing fines migration during irrigation. Critical for any ore with significant fines content.
Why Agglomerate
Fine ore particles (under 100 mesh) tend to migrate downward during leach irrigation, plugging the heap and creating impermeable layers. Once a heap loses permeability, solution channels around the blocked zones — leaving gold un-leached. Agglomeration prevents this by stabilizing fines onto coarser particles.
How It's Done
Crushed ore is dropped into a rotating drum (typically 2–4 m diameter, 10–20 m long), where cement (5–10 kg/t) and/or lime (1–3 kg/t) are added along with water. The tumbling action bonds fines to coarse particles. Cure time (24–72 hours) hardens the agglomerates before stacking.
Pulp Agglomeration
For very fine ores, KCA has delivered pulp-agglomeration circuits (Dolores, Mexico — $53M EPCM). Pulp agglomeration uses a thicker slurry feed and produces denser agglomerates suitable for unusually fine-grained orebodies that wouldn't respond to dry agglomeration.
Design Parameters
Cement dose, water content, drum speed, residence time, and curing schedule. All driven by laboratory column tests on agglomerated samples — KCA's Reno lab routinely runs agglomeration optimization as part of bankable feasibility-level testing.
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