Core Principle
Alluvial gold plants are designed to separate gold from sand, gravel, and clay using gravity concentration and water washing. They are essentially advanced, mechanized versions of the traditional gold pan.
Standard Process Flow & Key Machines
Here's the typical sequence, from feeding raw material to producing gold:
1. Feeding & Scrubbing
Purpose: To break up clay, agglomerates, and wash the gravel to liberate gold particles.
Key Machines:
Hopper & Grizzly: A steel hopper with a grizzly (bar screen) on top. The grizzly removes oversized rocks (>75-100mm) before material enters the plant.
Scrubber / Trommel Screen: This is a rotating drum that aggressively washes and breaks down the material. Inside are lifters and high-pressure water jets.
scrubber trommel
Trommel: Has a screen section to classify size as it scrubs.
Scrubber: Often used with a separate vibrating screen.
Rotary Scrubber
Trommel Screen
2. Screening & Classification
Purpose: To split the feed into different size fractions (e.g., coarse gravel, medium sands, fine sands). Gold is typically in the finer to medium sand fractions.
Key Machines:
Vibrating Screen: Most common. Different screen deck meshes (e.g., 10mm, 2mm, 1mm) separate the material. Oversize (worthless gravel) is conveyed to a waste pile.
3. Concentration (The Heart of the Plant)
Purpose: To separate heavy gold from lighter sands using gravity.
Key Machines (often used in combination):
Jig Machine: Excellent for coarse to medium gold (+1mm). Pulsating water creates a "bed" of heavy material (gold, black sands) at the bottom, which is collected periodically.
Jig Machine
Centrifugal Concentrator (Knelson / Falcon Type): The industry standard for fine gold recovery. Uses a spinning bowl and water fluidization to trap extremely fine gold particles. Highly efficient but requires continuous concentrate clean-up.
Centrifugal Concentrator
Spiral Concentrators: Simple, low-energy devices for pre-concentration. Slurry flows down a spiral trough; heavier particles move to the inner edge.
Shaking Tables: A classic, precise concentrator. Used for final upgrade of concentrates from other machines. A vibrating deck separates particles by density and size.
Spiral Concentrator
Gold Sluice Box: The simplest device. A lined trough with riffles that trap gold as slurry flows over it. Used in small operations or as a scavenger unit.
Vibrating gold sluice
4. Tailings & Water Management
Purpose: To recycle water and responsibly dispose of waste (tailings).
Key Machines:
Water Pumps & Piping: High-volume pumps to move slurry.
Sump Tanks & Settling Ponds: Allow solids to settle so clean(er) water can be recycled back to the plant. Crucial for environmental compliance.
5. Security & Clean-up
Purpose: To secure the gold and perform the final separation.
Key Machines/Areas:
Secure Room: Concentrates from jigs, centrifuges, etc., are brought here for final processing.
Gemini Table / Shaking Table: A small, precise shaking table to create a super-clean gold concentrate.
In summary, an alluvial gold plant is a modular washing and gravity separation system. The specific combination of machines is tailored to the characteristics of the deposit to achieve maximum gold recovery efficiently and responsibly.
