Ore treatment and beneficiation for gold mining is a multi-stage complex process involving the comprehensive application of physical, chemical and metallurgical technologies. The following are the main process flows and the equipment required, which are described in order and in stages:
Ore pre-treatment stage
1. Crushing
● Purpose: Crushing large pieces of raw ore to a particle size suitable for subsequent processing (usually ≤25mm).
Equipment:
● Coarse crushing: jaw crusher or gyratory crusher.
● Medium and fine crushing: cone crusher or impact crusher.
2. Grinding
● Purpose: Grind the ore further to a finer particle size (usually ≤0.074mm) to release gold minerals.
Equipment:
● Ball mill, rod mill or semi-autogenous mill (SAG mill).
● Classification equipment: hydrocyclone or spiral classifier.
2. Ore dressing stage
① Gravity separation
● Applicable ore: coarse gold (such as placer gold or natural gold in quartz veins).
Process flow:
● Jig to separate high-density gold particles.
● Shaking table or spiral chute for further enrichment.
● Advantages: low energy consumption, environmental protection, suitable for early roughing.
② Flotation
● Applicable ore: fine-grained disseminated sulfide ore (such as gold-bearing pyrite, arsenopyrite).
Process flow：
● Add collector (such as xanthate) and frother to make the gold-bearing minerals float with bubbles in the flotation machine.
● Equipment: mechanical agitation flotation machine, aerated flotation machine.
③ Cyanide leaching
● Applicable ore: oxidized ore or difficult-to-treat sulfide ore (pre-treatment oxidation is required).
Process flow:
● Heap leaching: low-grade ore is stacked, sodium cyanide solution (NaCN) is sprayed, and gold is dissolved into a complex.
● Tank leaching: high-grade ore reacts with cyanide in an agitator tank.
● Key equipment: heap leaching field, agitator leaching tank, safety protection system (leakage prevention, tail gas treatment).
④ Pretreatment technology (for difficult-to-treat ores)
● Roasting oxidation: high temperature decomposition of sulfide minerals to release encapsulated gold.
● Biological oxidation: use microorganisms (such as Thiobacillus ferrooxidans) to decompose sulfides.
● High-pressure oxidation (POX): oxidize sulfides under high temperature and pressure.
3. Gold extraction and refining
① Activated carbon adsorption (CIP/CIL process)
● Process: Gold in the cyanide leachate is adsorbed by activated carbon in the form of Au(CN)₂⁻, and then desorbed by high temperature.
● Equipment: adsorption tank, desorption electrolysis system, activated carbon regeneration furnace.
② Zinc powder replacement (Merrill-Crowe Process)
● Process: Add zinc powder to the leachate to replace the gold mud
③ Electrolytic refining (Electrowinning)
● Process: Electrolytically deposit gold on the cathode to obtain gold ingots with a purity of ≥99.5%.
● Equipment: electrolytic tank, stainless steel cathode plate, rectifier.
④ Fire refining
● Process: Gold mud smelting (above 1200°C), adding flux such as borax, and separating impurities.
● Equipment: induction melting furnace, casting mold.
4. Tailings treatment and environmental protection
● Tailings pond: storage of leaching residue and flotation tailings, requiring anti-seepage treatment.
● Cyanide degradation: use hydrogen peroxide (H₂O₂) or SO₂/air method to destroy residual cyanide.
● Wastewater circulation: closed-circuit water system reduces emissions and recycles water and reagents.
5. Special ore treatment
● Telluride gold ore: roasting or wet oxidation is required to decompose the telluride.
● Carbonaceous gold ore: pre-oxidation or adding agents to inhibit carbon adsorption.
● Fine-grained gold ore: resin adsorption (RIP) or thiourea leaching is used instead of cyanide.
6. Key Equipment List
| Phase |
Equipment Examples |
| Crushing |
Jaw crusher, cone crusher |
| Grinding |
Ball mill, hydrocyclone |
| Gravity separation |
Shaker, centrifugal separation machine |
| Flotation |
Flotation machine, automatic dosing system |
| Leaching |
Stirred leaching tank, heap leaching field |
| Adsorption/desorption |
CIP/CIL adsorption tower, desorption electrolysis device |
| Smelting |
Electric arc furnace, casting production line |
7. Basis for process selection
● Ore properties: gold occurrence state (free/encapsulated), particle size, paragenetic minerals.
● Economic efficiency: The grade determines whether to use high-cost processes (such as biological oxidation).
● Environmental regulations: Non-cyanide processes (such as thiosulfate leaching) are preferred in areas where cyanide use is restricted.
By optimizing the process combination (such as the combined process of "gravity separation + flotation + cyanidation"), the recovery rate can be maximized (usually 85%~95%). Modern mines also tend to use digital control (such as online analyzers, AI-optimized reagent addition) to improve efficiency.
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