Overview
The Fort Knox Mine operates two distinct gold recovery circuits: a conventional mill processing line and a run-of-mine heap leaching operation. The facility processes free-milling gold ore through crushing, grinding, cyanide leaching, and carbon adsorption circuits, with final gold recovery through electrowinning and doré bar production.
Key Process Stages
- Mill Processing Line (36,287 t/d capacity): Primary crushing (1.52×2.59 m gyratory crusher), SAG milling (10.4×4.6 m with 2×7,000 hp motors), ball milling (2×6.1×9.1 m mills), gravity concentration (Knelson concentrators), cyanide leaching (7×94,000 gallon tanks), and CIP recovery
- Heap Leach Operations: Valley-fill dump leaching (Walter Creek and future Barnes Creek pads) with 15m lifts, year-round irrigation, and parallel CIC circuits (61,000 L/m capacity)
- Gold Recovery: Carbon stripping, electrowinning, and doré bar production at centralized refinery
- Tailings Management: Detoxification of mill tailings before TSF deposition; permanent on-pad storage for heap leach residues
Critical Data
| Parameter | Value |
|---|---|
| Mill Throughput | 36,287 t/d (40,000 stpd) |
| Primary Crusher Capacity | 65,317 t/d (72,000 stpd) |
| Gold Recovery | 81-83% (mill), variable (heap) |
| Cyanide Concentration | 0.15 kg/solution tonne |
| Power Consumption | 300,000 MWh/yr (mill), 80-90,000 MWh/yr (heap) |
| Water Consumption | 5.7 Mm³ annually |
| Lime Consumption | 0.33 kg/tonne ore |
| Carbon Consumption | 0.0014 kg/tonne solution |
Circuit Features
The mill features advanced gravity recovery (Acacia reactor) for coarse gold and a seven-stage leach-CIP circuit. The heap leach operation uses innovative buried drip irrigation for year-round operation in Alaska’s climate. Both circuits share centralized gold recovery infrastructure with carbon elution and electrowinning capacity.
Future Operations
Following mill closure in 2020 due to TSF constraints, all ore will transition to heap leaching on the new Barnes Creek pad, maintaining gold production through the carbon-in-column recovery system.
